C Norman Bartlett says that gentleness (or meekness)...

Eadie writes...

This Christian grace is universal in its operation—submission Godward, meekness manward, which seems to be its special reference. (Eadie, John: Epistle of St Paul to the Galatians)

In Greek literature prautes was sometimes used of a feigned, hypocritical concern for others that is motivated by self-interest. But in the New Testament it is always used of genuine consideration for others.

Prautes denotes the humble and gentle attitude which expresses itself, in particular, in a patient submissiveness to offense, free from malice and desire for revenge...controlled strength, the ability to bear reproaches and slights without bitterness and resentment; the ability to provide a soothing influence on someone who is in a state of anger, bitterness and resentment against life...the word indicates an obedient submissiveness to God and His will, with unwavering faith and enduring patience displaying itself in a gentle attitude and kind acts toward others, and this often in the face of opposition. It is the restrained and obedient powers of the personality brought into subjection and submission to God’s will by the Holy Spirit (Gal 5:23)....the opposite of arrogance...the word stands in contrast to the term orge (wrath, anger as a state of mind)...It denotes the humble and gentle attitude which expresses itself, in particular, in a patient submissiveness to offense, a freedom from malice and desire for revenge...mildness, patient trust in the midst of difficult circumstances. (2Co 10:1) (Compiled from the Linguistic and Exegetical Key to the Greek NT)

Prautes was used in secular Greek writings to describe a soothing wind, a healing medicine, and a colt that had been broken. In each instance, there is power for a wind can become a storm, too much medicine can kill and a horse can break loose.

The Greeks used prautes to describe strong animals that were brought under control, Xenophon writing that horses that work together are more likely to “stand quietly” together. Aristotle wrote of the “easy-tempered and easily domesticated” elephant. Plato described a mighty and strong beast which could be tamed and fed by a man who learned how to handle it.

Thus prautes describes power under control. Just as wisdom is the right use of knowledge, so gentleness is the right use of authority and power.

Prautes is an interesting word. Aristotle defined it as the correct mean between being too angry and being never angry at all. It is the quality of the man whose anger is so controlled that he is always angry at the right time and never at the wrong time. It describes the man who is never angry at any personal wrong he may receive, but who is capable of righteous anger when he sees others wronged.

The meek person does not have to fly off the handle because he has everything under control. A perfect picture is found in our Lord Jesus Christ. Quoting from the Septuagint (LXX = Greek of the Hebrew Old Testament) rendering of Zechariah 9:9, which predicts the Lord’s triumphal entry into Jerusalem, Matthew uses the adjective form of prautes (praus) to describe Jesus as

“gentle (praus) and mounted on a donkey, even on a colt, the foal of a beast of burden” (Mt 21:5).

In a gracious appeal to His followers, Jesus used the same adjective of Himself, saying,

“Take My yoke upon you, and learn from Me, for I am gentle ((praus) and humble in heart; and you shall find rest for your souls” (Mt 11:29).

James uses prautes in his discussion of a teachable spirit instructing his readers to

Barclay comments on this verse writing that this man

will receive the word with gentleness. (humility = praǘtēs). Gentleness is an attempt to translate the untranslatable word praǘtēs. This is a great Greek word which has no precise English equivalent. Aristotle defined it as the mean between excessive anger and excessive angerlessness; it is the quality of the man whose feelings and emotions are under perfect control. Andronicus Rhodius, commenting on Aristotle, writes, “Praǘtēs is moderation in regard to anger … You might define praǘtēs as serenity and the power, not to be lead away by emotion, but to control emotion as right reason dictates.” The Platonic definitions say that praǘtēs is the regulation of the movement of the soul caused by anger. It is the temperament (krasis) of a soul in which everything is mixed in the right proportions. No one can ever find one English word to translate what is a one word summary of the truly teachable spirit. The teachable spirit is docile and tractable, and therefore humble enough to learn. The teachable spirit is without resentment and without anger and is, therefore, able to face the truth, even when it hurts and condemns. The teachable spirit is not blinded by its own overmastering prejudices but is clear-eyed to the truth. The teachable spirit is not seduced by laziness but is so self-controlled that it can willingly and faithfully accept the discipline of learning. Praǘtēs describes the perfect conquest and control of everything in a man’s nature which would be a hindrance to his seeing, learning and obeying the truth. (Barclay, W: The Daily Study Bible Series, Rev. ed. Philadelphia: The Westminster Press)

James in the context of discussion the control of one's tongue again uses praǘtēs in his answer to the rhetorical question

Who among you is wise and understanding (mental perception and comprehension)? Let him show (expose to the eyes, giving evidence or proof of it) by his good behavior his deeds in the gentleness (praǘtēs) of wisdom (the ability to view life from God’s perspective). (Js 3:13)

We can perceive understanding in others quite easily, but wisdom is more difficult to identify. James said to look at a person’s behavior if you want to see if he or she is wise. In other words if a man or woman is wise and understanding, they will demonstrate it by their good conduct coupled with the gentle spirit that comes from godly wisdom. The wisdom James had in mind did not result so much in what one thinks or says but in what one does. One of the marks of godly wisdom is praǘtēs -- gentleness, meekness or humility.

Knowledge is proud that she has learned so much. Wisdom is humble that she knows no more.”

Constable in his note on this verse adds that

The Greek word praǘtēs (“gentleness”) occurs in non-biblical literature to describe a horse that someone had broken and had trained to submit to a bridle. It pictures strength under control, specifically the Holy Spirit’s control. The evidence of this attitude is a deliberate placing of oneself under divine authority. The only way to control the tongue is to place one’s mind deliberately under the authority of God and to let Him control it . (Constable, T . Thomas Constable's Expository Notes on the Bible)

A believer's attitude toward unbelievers should always reflect a spirit of gentleness, being indulgent toward the infirmities of the unsaved. Peter writes that even when unbelievers intimidate us we should still

“sanctify Christ as Lord in your hearts,“always being ready to make a defense to everyone who asks you to give an account for the hope that is in you, yet with gentleness (prautes) and reverence” (see note 1 Peter 3:15)

and “with gentleness (prautes)   correcting those who are in opposition (could refer to unbelievers or rebellious unbelievers), if perhaps God may grant them repentance leading to the knowledge of the truth” (see note 2 Timothy 2:25).

Those "who are spiritual" are to deal with disobedient fellow believers “in a spirit of gentleness (prautes)” (Gal 6:1). How is this possible? Paul had just written that

the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness,  gentleness (prautes), self-control; against such things there is no law. (Gal 5:22-23)

It follows that the Spirit filled/controlled believer is the one most suited to "restore (a man caught in trespass) in a spirit of gentleness."

Meekness is that unassuming inner spirit of mildness and gentleness which is the opposite of haughtiness, harshness and self-assertiveness.

Meekness is a willingness to waive one's rights for a good cause, just as Jesus waived His rights to His rule as King as he rode into Jerusalem mounted on a donkey (see above). Set aside your rights! Do not demand that you be satisfied, but for the sake of the gospel of Jesus Christ be willing to suffer loss. Meekness is the opposite of rudeness and abrasiveness.

Ray Stedman describes meekness as "strength under control" adding that

It is real strength, but it does not have to display itself or show off how strong it is. This is what our Lord beautifully displayed He described himself as "meek and lowly in heart." The first curriculum of the Holy Spirit is that we must do what Jesus said, "take my yoke upon you and learn of me, for I am meek and lowly of heart."

Meekness and weakness are not synonymous. Meekness says,

"God, in this situation, You have a purpose. You're in control, sovereign, and ruling over all."

Meekness is seeing everything as coming from God and accepting it without murmuring and without disputing, patiently submitting to any and every offense, without any desire for revenge or retribution!

Barclay says the best illustration of prautes is the watchdog

who is bravely hostile to strangers and gently friendly with familiars whom he knows and loves.

“is closely linked with humility, and follows directly upon it (see Eph 4:2-note; Col 3:12-note) because it is only the humble heart which is also the meek; and which, as such, does not fight against God, and more or less struggle and contend with Him. This meekness, however, being first of all meekness before God, is also such in the face of men, even of evil men, out of a sense that these, with the insults and injuries which they may inflict, are permitted and employed by Him for the chastening and purifying of His elect. This was the root of David’s (meekness) when Shimei cursed and flung stones at him—the consideration that the Lord had bidden him (2Sa 16:11), that it was just for him to suffer these things, however unjustly the other might inflict them; and out of like convictions all true Christian (meekness) must spring. He that is meek indeed will know himself a sinner among sinners...and this knowledge of his own sin will teach him to endure meekly the provocations with which they may provoke him, and not withdraw himself from the burdens which their sin may impose (Ibid)

Barclay adds that prautes

"describes the man whose temper is always under complete control. He knows when to be angry and when not to be angry. He patiently bears wrongs done to himself but is ever chivalrously ready to spring to the help of others who are wronged." (Ibid)

F B Meyer has a devotional based on 2 Timothy 2:24 (note) entitled "The Fruit of the Spirit - Gentleness"

IT IS not easy to cultivate this fruit of the Spirit because it has many counterfeits. Some people are naturally easy-going, devoid of energy and ambition, at heart cowardly, or in spirit mean. Many of us are characterized by a moral weakness and decrepitude that make it easy for us to yield rather than contest in the physical or intellectual arena.

But in gentleness there must be the consciousness of a considerable reserve of force. The gentleness of God is combined with omnipotence. The movements of creation, in which there is neither voice nor language, prove the infinite forces which are at work. When a boy is trying to lift or carry a heavy beam, as likely as not there will be a great crash when he reaches the end of his task, and puts it on the ground. His strength is so nearly exhausted that he is only too glad to get rid of his burden, anyhow, and at any cost. But if a strong man shoulders the same burden, and carries it for the same distance, he puts it down gently, because he has not taxed his strength and has plenty left.

It is the prerogative of great strength to be gentle. Always remember that you are linked with the Infinite God, and that all things are possible to you. There must also be infinite pity. We must be tolerant and pitiful to those who abuse us, or have been embittered by disappointment, or have been ill-used. It must be our aim to make allowances for such, and always to be sweetly reasonable towards any brusqueness, rudeness and bad manners of their behaviour. Let us be willing to admit that much is due to congenital moroseness. Therefore, we bear gently with the erring, and with those who are out of the way, because we also are encompassed with infirmity.

It is necessary also that there should be a deep humility. Thomas a Kempis says: "If thou wilt be borne with, bear also with another. Endeavour to be patient in bearing with the defects and infirmities of others, what sort soever they be: for that thyself also hast many failings which must be borne by others." Our resentment against others should be always tempered by our remembrance of our own sins. So shall we be God's own gentlefolk.

PRAYER - O God, our behaviour has not manifested all the fruits of the Spirit, or been full of the graciousness and gentleness of Christ. Forgive us, and enable us so to live that His beauty may be on our faces, the tone of His voice in our speech, the gentleness of His tread in our steps, the unselfishness of His deeds in our hands. AMEN. (F B Meyer. Our Daily Walk)

Socrates regarded egkrateia as a cardinal virtue and Philo described it as superiority expressed in self-restraint. 

Greeks used this term especially to describe one who had his sexual passions under control, but the NT extends the meaning to all areas of life where the discernment between good and evil is important (cf 1Th 5:21-22).

In his first epistle to the Corinthians (who lived in a "sex crazed" society) Paul uses the related verb egkrateuomai writing that...

if (the unmarried) do not have self-control, let them marry; for it is better to marry than to burn (to seethe inwardly with destructive lusts). (1Corinthians 7:9)

Paul implies that one needs to exercise self control in regard to sexual behavior, which is quite applicable to believers in America, where even the commercials have become "R rated" and filled with sexual innuendos! In the present context however the self control is not just in the area of sexuality but in any area where one needs to exercise restraint (e.g., drunkenness, carousing and things like these...)

By temperance is meant self-control in the broadest and fullest sense of the term. We need to go into training for CHRIST and to keep ourselves spiritually fit at all times, for we never know when a critical test may come or a golden opportunity arise that will call upon our spiritual reserves. To this end we should be prepared to give up whatever mars our witness and hinders usefulness in the Master’s service. Attaining to the best may necessitate abstaining from the rest. The lesser must sometimes be sacrificed to the higher good. (C. Norman Bartlett: Galatians and You: Studies in the Epistle of Paul to the Galatians, 1948)

Brian Bill writes that...

Nestled among the Spirit’s produce is the seemingly out-of-place fruit of self-control. This characteristic of a Christ-follower seems to focus more on me instead of on my relationships with other people. I can exercise self-control when I’m the only person in the house. In fact, sometimes the hidden, private moments when no one else is looking is precisely when I need self-control the most. However, if we properly exercise the fruit of self-control, it will benefit those around us. In some ways, we might consider this virtue the most important because without self-control the works of the flesh cannot be overcome and the other elements of the Fruit of the Spirit will not be evident.

When the Greeks wanted to illustrate self-control, they built a statue of a man or a woman in perfect proportion. To them, self-control was the proper ordering and balancing of the individual. (Galatians 5:23 Seizing Self-Control)

In the ancient world, self-control characterized athletes who sought to be self-restrained and self-disciplined, qualities which were crucial in their quest for victory in the intense competition of the elite Olympic Games.

In 1 Corinthians 9 Paul used the cognate verb egkrateuomai to describe the attitude believers need in order to win the prize, comparing them to Olympic athletes explaining that...

everyone who competes in the games exercises self-control (egkrateuomai) in all things (How many things? Why do they do this?). They then do it to receive a perishable wreath, but we an imperishable ("Chew the cud of this contrast for a moment." - in other words Meditate). Therefore (after thinking about the contrast and remembering that believers are destined for eternity, let your mind come to the same conclusion and determination that Paul came to...) I run in such a way, as not without aim; I box in such a way, as not beating the air  but I buffet my body and make it my slave, lest possibly, after I have preached to others, I myself should be disqualified. (1Corinthians 9:25-27) (But be careful... remember Paul's running and boxing and buffeting were not a reflection of self effort but were grace based, Spirit empowered effort, for as he said elsewhere "by the grace of God I am what I am, and His grace toward me did not prove vain; but I labored [see meaning of kopiao] [this was Paul's and is every believer's responsibility] even more than all of them, yet not I, but the grace of God [God's "responsibility" - His sovereignly bestowed unmerited favor] with me [and also available to each and every believer]." 1Corinthians 15:10)

Paul  argues that athletes exercise self-control because they are motivated by a clearly defined goal and understand that in order to achieve that goal, they must (at least for a time) resist the distractions that originate from their bodily passions and desires.

In a similar way, believers are charged to control their flesh (not the physical body but the evil disposition that still lives in our mortal bodies), with its corrupt, deceptive passions and desires, rather than allowing themselves to be controlled by them. However, what is referred to as self-control is actually (and only) the result of letting the Spirit take control (Spirit enabled "self" control), so that one is walking in Him, walking by the Spirit, keeping in step with the Spirit.

Vincent adds this historical note on self control in ancient athletes

The candidate for the races was required to be ten months in training, and to practice in the gymnasium immediately before the games, under the direction of judges who had themselves been instructed for ten months in the details of the games. The training was largely dietary. Epictetus says: “Thou must be orderly, living on spare food; abstain from confections; make a point of exercising at the appointed time, in heat and in cold; nor drink cold water nor wine at hazard.” Horace says: “The youth who would win in the race hath borne and done much; he hath sweat and been cold; he hath abstained from love and wine” (“Ars Poetica,” 412). Tertullian, commending the example of the athletes to persecuted Christians, says: “Coguntur, cruciantur, fatigantur.” “They are constrained, harassed, wearied” (“Ad Martyres,” 3). Compare 2 Timothy 2:5 [note])

Paul's point is that each believer should be like a highly trained athlete who exercises control over his or her body (the seat of the strong desires) during the period in which they are training for the Olympics. While the athlete says "No" to these bodily desires in their own strength, in contrast, Spirit controlled believers are enabled to exercise supernatural self control in the strength of the Holy Spirit. When we say "Yes" to the Spirit, we cannot say "Yes" to the flesh for these are in opposition to one another (see note Galatians 5:17).

But I say, walk (present imperative = not a suggestion but a command to make it your lifestyle or your habitual practice to conduct all of the aspects of you life) by the Spirit and (here is the conditional promise - conditioned on choosing to walk by the Spirit) you will (absolutely) not carry out (not that you won't still experience them but that you won't act on them!) the (strong) desire of the flesh (see note Galatians 5:16).

The highly respected nineteenth century Scottish theologian John Eadie wrote that self control is...

He who is slow to anger is better than the mighty, and he who rules his spirit, than he who captures a city. (Proverbs 16:32)

Comment: Have you ever tried in your own strength (self effort) to control your temper or restrain the desire follow through with a sudden outburst of anger? I have and it might work for a moment, but Sin remains crouching at the door of my mind and heart just waiting for the opportunity to "pounce", and unfortunately it often does. How difficult is it for us to achieve victory in this area? The writer says that it is easier to gain a victory over a city (and in ancient times these were walled, well fortified cities, totally unlike our modern cities!) then to conquer one's temper! In my own strength I cannot control the overwhelming, powerful, compelling urge to lash out, but the Spirit of the Gentle Shepherd can control it as I yield my "rights" to Him and rest in His sufficiency to enable me to work out my salvation in the area of "Anger Management 101" (recall Paul's power in 1 Corinthians 15:10 quoted above).

Paul uses egkrateia in his appearance before Felix, and in this context apparently referring to self–control in the area of sex. It is indeed fascinating that Paul's presentation of the gospel emphasized self control. As Paul spoke before the Roman governor Felix and his wife Drusilla, he spoke of...

righteousness, self–control and the judgment to come, (and) Felix became frightened and said, ‘Go away for the present, and when I find time, I will summon you’ ” (Acts 24:24-25).

Felix had stolen Drusilla from her former husband and was therefore living with her in an adulterous relationship. The sexual self–control of which Paul spoke pertained to lustful passion, and Felix clearly understood Paul's warning. The message to the governor was that he was living contrary to God’s righteousness by refusing to discipline his sexual desire, and for that he was subject to God’s judgment.

Pastor Brian Bill adds that...

Felix was no different than many others in the Roman Empire. Scholars tell us that when ancient Rome was disciplined and controlled, it was a great nation, but when it became saturated in its own sin it lost its glory. Drunkenness, orgies, and an “anything goes” mindset caused Rome to cave inward and implode upon itself. The decline of the Roman Empire went hand-in-hand with self-indulgence. I wonder if America is going down that same road? (Galatians 5:23 Seizing Self-Control)

Barclay says

Egkrateia is that great quality which comes to a man when Christ is in his heart, that quality which makes him able to live and to walk in the world, and yet to keep his garments unspotted from the world.

Self-control means mastering one’s emotions rather than being mastered by them.  Lack of self control played a significant role in abominable deeds of the false teachers Peter exposed in chapter 2 of his second epistle.

For speaking out arrogant words of vanity they (the false teachers) entice by fleshly desires (What manner of "desires"? Those that originate in the fallen flesh), by sensuality, those who barely escape from the ones who live in error, promising them freedom while they themselves are slaves of corruption; for by what a man is overcome, by this he is enslaved (perfect tense - speaks of the permanence of this bondage). (See notes 2 Peter 2:18; 19)

Sow a thought, reap an action.
Sow an action, reap a habit.
Sow a habit, reap a character.
Sow a character, reap a destiny!

The false teachers in 2 Peter claimed that "liberty" was a warrant for licentiousness rather than life as it should be lived in the Spirit. These men instead of self control were "sensuality controlled", enslaved to greed and fleshly desires. They believed and taught that knowledge freed people from the need to control their passions. Peter countered their false doctrine that claimed that knowledge emancipates men from the obligations of morality.

In another pithy proverb, Solomon gives a vivid picture of the danger of the lack of self-control writing...

Like a city that is broken into and without walls is a man who has no control over his spirit. (Proverbs 25:28)