Modified from Irving L. Jensen's excellent work "Jensen's Survey of the NT"

FOR THROUGH THE GRACE (gift) GIVEN TO ME  I SAY TO EVERY MAN (no believer excluded) AMONG YOU: Lego (1SPAI) gar dia tes charitos tes dotheises (APPFSG) moi panti to onti (PAPMSD) en humin:  (Ro 12:6, 7, 8; 1:5; 15:15,16; 1Corinthians 3:10; 15:10; Ephesians 3:2,4,7,8; 4:7, 8, 9, 10, 11, 12; Colossians 1:29; 1Timothy 1:14; 1Peter 4:11)

For (gar) explains that a proper opinion of oneself (i.e., to not to think more highly) is the immediate effect of a surrender to God, a non conforming to the world and a transformation produced by the renewing of our mind. Paul illustrates in his own person, in giving this advice, the rule he is laying down for the Church by emphasizing that what is communicating is "through the grace given" him and therefore without haughtiness or presumption. In addition note that Paul emphasizes that the truth he is communicating here is is a word to "every man" -- Everyone in the Body of Christ needs to hear and heed this message! No exceptions.

What is the "grace given to" Paul? Paul is alluding to his being an apostle and that this "grace" was only because God chose him to be an apostle. Paul had nothing to do with it as he reminded his beloved disciple Timothy in his last known written communication beginning the letter with acknowledgement that he was...

"Paul, an apostle of Christ Jesus by the will of God" (2 Timothy 1:1)

There were surely people associated with Paul who would have loved to have been an apostle, but God didn’t choose them. He chose Paul, a man who proved to be a channel through which His grace could bountifully flow as shown in many of his epistles...

For example, Paul reminded the Corinthian church that what he did, he did not do in his strength alone...

But by the grace of God I am what I am, and His grace toward me did not prove vain (fruitless and without effect); but I labored even more than all of them, yet not I, but the grace of God with me.  (1Cor 15:10, cp 2Cor 12:9, 10)

Paul testified in Galatians to the grace given to him...

(Speaking before the Jewish council at Jerusalem Paul declared that) He (the same God) who effectually worked for Peter in his apostleship to the circumcised effectually worked for me also to the Gentiles, and recognizing the grace that had been given to me, James and Cephas and John, who were reputed to be pillars, gave to me and Barnabas the right hand of fellowship, that we might go to the Gentiles, and they to the circumcised. (Galatians 2:8,9)

To the Ephesians Paul repeatedly emphasized the grace given to him writing...

2 if indeed you have heard of the stewardship of God's grace which was given to me for you;
3 that by revelation there was made known to me the mystery, as I wrote before in brief.
4 And by referring to this, when you read you can understand my insight into the mystery of Christ,
5 which in other generations was not made known to the sons of men, as it has now been revealed to His holy apostles and prophets in the Spirit;
6 to be specific, that the Gentiles are fellow heirs and fellow members of the body, and fellow partakers of the promise in Christ Jesus through the gospel,
7 of which I was made a minister, according to the gift of God's grace which was given to me according to the working of His power.
8 To me, the very least of all saints, this grace was given, to preach to the Gentiles the unfathomable riches of Christ, (Ephesians 3:2,4,7,8)

Writing to the Colossians of his great objective to present every man complete (mature, "full grown") in Christ, he explained that it was...

And for this purpose also I labor (to the point of weariness), striving (agonizing) according to His power (made available by His grace which is perfected in weakness), which mightily works within me (see notes on Colossians 1:29)

MacArthur explains the preposition "For" this way:
 

"For" indicates a transition from what the apostle has just commanded, tying spiritual service to spiritual dedication, the bridge between them being spiritual attitude. The Christian’s proper attitude is humility, not to think more highly of himself than he ought to think. Lack of that foundational virtue causes many believers to stumble. No matter how well grounded we may be in God’s Word, how theologically sound we may be, or how vigorously we may seek to serve Him, our gifts will not operate so that our lives can be spiritually productive until self is set aside. From self denial in the spiritual worship of God flows self surrender to the will of God, and from self surrender flows selfless service in the work of God." (emphasis added)

How fitting in this section on SERVICE that Paul begins with acknowledgement of the power for all God honoring service, God's grace, ("for through the grace given to me") a truth he continually reminded the saints of in his letters (cf Ro 1:5-note, Ro 15:15, 16- notes,1Co 3:10, 15:10,Ga 2:8, 9,Ep 3:2-note, Ep 3:7, 8-note, Ep 4:7-note,1Ti 1:14).

Remember that the practical section that follows is not possible apart from a presentation of ourselves to God (Ro 12:1, 2), once and for all and then each morning for the rest of our life.

Someone has well said that there are only two kinds of people in the world,  those who wake up in the morning and say, "Good morning, Lord," and those who wake up in the morning and say, "Good Lord, its morning!"

Let us seek to be among those who greet the day acknowledging He is Lord of the new day and I am His bondservant ready to do His will. It will make a radical difference in the way we respond to all the distractions, interruptions, harsh words, unfair treatment, etc that are part of life.

The evidence of a surrendered life then is an available body, a willingness to help, to put yourself out, to be expendable, to respond to the needs God's has placed in your life. The first place where this service becomes visible is in the church itself -- in the body of Christ. Therefore this section deals with living out the spiritual gift(s) (see study of charisma) God has given to every believer. However, before Paul gives specific instructions regarding spiritual gifts he prefaces it with an admonishment concerning humility, for he is fully aware of pride that is prone to arise from spiritual giftedness (1Co 8:2,10:12, Pr 16:18, Is 5:21) Remember also that spiritual giftedness does not necessarily equal spiritual maturity.
           
Stedman prefaces this section on service with this thought
 

I don't think the Christian life is worth a 'snap of the finger' if something exciting isn't happening from time to time. It really never begins for us until we begin to see that God intends to work through us individually, and that, when God is at work, things begin to happen. It isn't always some spectacular, outward display, but things take place...Once you discover this, as a result of the availability of the life-changing, transforming character of Christ dwelling in us, life becomes an exciting thing. You can hardly sleep at night, at times." The question for each of us then is " Is there anything you are excited about that God has done in your life recently?  (The Body at Work)

NOT TO THINK MORE HIGHLY OF HIMSELF THAN HE OUGHT (dei = necessary) TO THINK: me huperphronein (PAN) par o dei (3SPAI) phronein (PAN):  (Ro 11:20,25, Pr 25:27,26:12 Eccl 7:16, Mic 6:8, Lk 18:11 // 1Co 4:7, 8, 2Co 12:7, Ga 6:3, Php 2:3, 4, 5, 6, 7, 8, James 4:6,1Pe 5:5, 3Jn 9)

not to estimate himself above his real value" (Williams)

Think more highly (5252) (huperphroneo from huperphron = over-proud in turn from huper = above, over + phroneo = think) literally means to over think or think above and so to be haughty.

Alford renders the text

not to be high-minded above that which he ought to be minded, but to be so minded as to be sober-minded.

Or one might render it  “I say to everyone, do not super-think of yourself”. One can clearly see Paul's emphasis on the mind and specifically in context on what a renewed mind looks like (Ro 12:2).  

A believer should appraise the gifts God has given him fairly, glorifying God for their bestowal, and then exercise them through dependence upon the Holy Spirit and not in mock humility make light of them. A renewed mind thinks soberly about oneself.

An individual with a renewed mind comprehends that he or she is a member of a body, that every member of that body does not perform every function but that God gives each believer a specific spiritual gift ("function"). Therefore since we do not all have the same gifts, it logically follows that we need one another and one another's different gifts. Thinking more highly of ourselves than we ought to think is a universal tendency of the human race. Our old Adamic nature loves to over-think about itSELF.

As Denney notes:

“To himself, every man is in a sense the most important person in the world, and it always needs much grace to see what other people are, and to keep a sense of moral proportion.”

Our tendency to focus on self is the major cause for the deadly pestilence in the church (and the world) called "comparisonitis" —the tendency to measure one’s worth by comparing oneself to others. Do you look down on others and think highly of yourself because you possess a more "showy" spiritual gift than they? Paul's antidote for comparisonitis is not to see ourselves as we stack up against others, but to exercise sound judgment. What needs to change in your self assessment for you to judge yourself soberly? Jesus parable in (Lu 18:9-14) illustrates the deadly nature of comparisonitis and it therefore behooves us to diligently heed Paul's instruction.
           
Kent Hughes has these thoughts on 2 ways high minded thinking is manifest:

"This can take two classic forms. Primarily it is that of the self-elevating braggart—the person who tells you how smart he is, how much he has done, how strong he is, how rich he will be when he gets his big break—legends in their own mind....The other form of overestimation is more subtle—that of self-deprecating...those who self-consciously talk about themselves as if they were nobodies. I remember Dr. Lloyd-Jones telling of being at a train station where a man met him and said, “Oh, Dr. Jones, I am just a chimney sweep in the house of the Lord. Let me carry your suitcase. I am a nobody, and you are a man of great gifts.” Dr. Jones saw through the man immediately and did not deal too kindly with him. When a person acts like this, his expectation is that you will correct him. “No, no, you are really a great person.” (The way to expose [him] is to say, “You know, I think you’re right!”)"

Hughes adds this insightful summary:

The thought chain of Romans is compelling...
 

BUT TO THINK SO AS TO HAVE SOUND JUDGMENT: alla phronein (PAN) eis to sophronein:  (TTT topic on "sobriety") (1 Timothy 2:9,15; Titus 2:2,4,6,12; 1 Peter 1:13; 4:7; 5:8 )

but to rate his ability with sober judgment. (Amplified)

but try to have a sane estimate of your capabilities.  (Phillips)

Sound judgment (4993) (sophroneo from sozo [Vine] = saved, healed, whole + phren =  faculty of perceiving and judging) literally pictures one possessing a "saved" mind. It means to be of sound mind and thus able to think in a sane manner (Mk 5:15, Lk 8:35). In other contexts the idea is to use good sense and especially in regard to self control or "keeping one's head".

Related topics: in depth study on sozo; in depth study on related word sound mind = sophronismos

Here are the 6 NT uses of sophroneo - Mk 5:15 (demon possessed man now healed); Lk 8:35 (healed of demon possession); Ro 12:3; 2Co 5:13; Titus 2:6-note (a sound mind is a self controlled mind); 1Pe 4:7-note(in light of the end of all things)

The idea of  sophroneo is to "be in one's right mind" (2Co 5:13).

Luke records that after Jesus had entreated the demons out of the demoniac...

the people went out to see what had happened; and they came to Jesus, and found the man from whom the demons had gone out, sitting down at the feet of Jesus, clothed and in his right (sound) mind (sophroneo); and they became frightened. And those who had seen it reported to them how the man who was demon-possessed had been made well. (Lu 8:35, 36)

In a nutshell then Paul is advocating sober thought instead of "super-thought"!.

A T Robertson adds that in a sense

"self conceit is here treated as a species of insanity."

A right estimate of oneself will always be a humble estimate (cf Ga 6:3, 4, 5), a recognition that, in ourselves, we can do nothing (Jn 15:5), but that in Christ we can be used to the glory of God (Jn 15:8).  In context Paul is addressing one's attitude toward spiritual gifts. He wants us not to consider our gift to be of greater importance then another saint's gift but to have a humble attitude, an attitude which when you know you have it, you have lost it! Humility  (TTT, NTB) means putting Christ first, others second, and self last ("J.O.Y." is Jesus, then Others, finally Yourself). Humility  (TTT, NTB) is a lack of pre-occupation with self.

Sound judgment understands that

"Every good thing given and every perfect gift is from above, coming down from the Father of lights, with whom there is no variation or shifting shadow" (see note James 1:17)

This realization serves as a corrective against self-complacency and pride. What room for glorying is there in that which we have received?  Such “sober judgment” not only excludes an exaggerated opinion of oneself, but also warns us not to underestimate the abilities God has given us. Sometimes a false modesty may be just as detrimental to the church as pride.

Matthew Henry adds
 

"We must not say, I am nothing, therefore I will sit still, and do nothing; but, I am nothing in myself, and therefore I will lay out myself to the utmost, in the strength of the grace of Christ." (emphasis added)

Wiersbe adds that
 

"Each Christian must know what his spiritual gifts are and what ministry (or ministries) he is to have in the local church. It is not wrong for a Christian to recognize gifts in his own life and in the lives of others. What is wrong is the tendency to have a false evaluation of ourselves. Nothing causes more damage in a local church than a believer who overrates himself and tries to perform a ministry that he cannot do. (Sometimes the opposite is true, and people undervalue themselves. Both attitudes are wrong.)"

AS GOD HAS ALLOTTED TO EACH A MEASURE OF FAITH: hekasto os o theos emerisen metron pisteos: (Ro 12:6; John 3:34; 1 Corinthians 4:7; 12:7, 8, 9, 10, 11; 2 Corinthians 12:13; Ephesians 4:7,13,16)

Measure of faith conveys the truth that each believer can know