2Corinthians 12 is a very intersting chapter and there are many questions and interpretations about it.
Was Paul speaking of Himself or perhaps John when he spoke of the man who went up to heaven?
What was Paul's afflection?
Was Paul that insecure about himself and those that he preached too? how worried was he that his message had fallen because of His past?
How bad were things in Corinth?
THe whole point of the passage is, IMO, that boasting about what one has seen, that one has been chosen, the persecutions one has endured ( as he had written about in the past) was NOT correct. That, as Paul said, "Boast only of the Lord" ( Paraphrasing).
Paul believed that because of his arrogance He was given an afflection and that this was to be like a "messenger from Satan" to remind him always of thge price of arrogance.
2 Corinthians 12
New American Standard Bible (NASB)
Paul’s Vision
12 Boasting is necessary, though it is not profitable; but I will go on to visions and revelations of the Lord. 2 I know a man in Christ who fourteen years ago—whether in the body I do not know, or out of the body I do not know, God knows—such a man was caught up to the third heaven. 3 And I know how such a man—whether in the body or apart from the body I do not know, God knows— 4 was caught up into Paradise and heard inexpressible words, which a man is not permitted to speak. 5 On behalf of such a man I will boast; but on my own behalf I will not boast, except in regard to my weaknesses. 6 For if I do wish to boast I will not be foolish, for I will be speaking the truth; but I refrain from this, so that no one will credit me with more than he sees in me or hears from me.
A Thorn in the Flesh
7 Because of the surpassing greatness of the revelations, for this reason, to keep me from exalting myself, there was given me a thorn in the flesh, a messenger of Satan to torment me—to keep me from exalting myself! 8 Concerning this I implored the Lord three times that it might leave me. 9 And He has said to me, “My grace is sufficient for you, for power is perfected in weakness.” Most gladly, therefore, I will rather boast about my weaknesses, so that the power of Christ may dwell in me. 10 Therefore I am well content with weaknesses, with insults, with distresses, with persecutions, with difficulties, for Christ’s sake; for when I am weak, then I am strong.
11 I have become foolish; you yourselves compelled me. Actually I should have been commended by you, for in no respect was I inferior to the most eminent apostles, even though I am a nobody. 12 The signs of a true apostle were performed among you with all perseverance, by signs and wonders and miracles. 13 For in what respect were you treated as inferior to the rest of the churches, except that I myself did not become a burden to you? Forgive me this wrong!
14 Here for this third time I am ready to come to you, and I will not be a burden to you; for I do not seek what is yours, but you; for children are not responsible to save up for their parents, but parents for their children. 15 I will most gladly spend and be expended for your souls. If I love you more, am I to be loved less? 16 But be that as it may, I did not burden you myself; nevertheless, crafty fellow that I am, I took you in by deceit. 17 Certainly I have not taken advantage of you through any of those whom I have sent to you, have I? 18 I urged Titus to go, and I sent the brother with him. Titus did not take any advantage of you, did he? Did we not conduct ourselves in the same spirit and walk in the same steps?
19 All this time you have been thinking that we are defending ourselves to you. Actually, it is in the sight of God that we have been speaking in Christ; and all for your upbuilding, beloved. 20 For I am afraid that perhaps when I come I may find you to be not what I wish and may be found by you to be not what you wish; that perhaps there will be strife, jealousy, angry tempers, disputes, slanders, gossip, arrogance, disturbances; 21 I am afraid that when I come again my God may humiliate me before you, and I may mourn over many of those who have sinned in the past and not repented of the impurity, immorality and sensuality which they have practiced.