Thorn in the flesh (Paul)

And lest I should be exalted above measure through the abundance of the revelations, there was given to me a thorn in the flesh, the messenger of Satan to buffet me, lest I should be exalted above measure. For this thing I besought the Lord thrice, that it might depart from me. And he said unto me, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me. Therefore I take pleasure in infirmities, in reproaches, in necessities, in persecutions, in distresses for Christ's sake: for when I am weak, then am I strong.

2 Cor 12:7-10:

Many interpretations have been given of Paul's meaning:

1. This phrase is a Judaism; an expression used in the Old Testament in Numbers 33:55 "But if ye will not drive out the inhabitants of the land from before you; then it shall come to pass, that those which ye let remain of them shall be pricks in your eyes, and thorns in your sides, and shall vex you in the land wherein ye dwell." In Second Corinthians 7:12, the messenger of Satan is a spirit of persecution which followed Paul, hence it was a "thorn in his flesh". It does not denote any physical symptom or spiritual failing on Paul's part.
2. Some Roman Catholic writers think that it denotes suggestions to impiety.
3. Martin Luther, John Calvin, and other Reformers interpret the expression as denoting temptation to unbelief.
4. Others suppose the expression refers to "a pain in the ear or head," epileptic fits, or, in general, to some severe physical infirmity, which was a hindrance to the apostle in his work (comp. 1 Cor. 2:3; 2 Cor. 10:10; 11:30; Gal. 4:13, 14; 6:17). It has been suggested that his malady was a defect of sight caused the dazzling light which shone around him at his conversion. This would account for the statements in Gal. 4:14; 2 Cor. 10:10; also Acts 23:5, and for his generally making use of the help of an amanuensis (comp. Rom. 16:22, etc.).
5. Another view which has been maintained is that this "thorn" consisted in an infirmity of temper, to which he occasionally gave way, and which interfered with his success (comp. Acts 15:39; 23:2-5). If we consider the fact, "which the experience of God's saints in all ages has conclusively established, of the difficulty of subduing an infirmity of temper, as well as the pain, remorse, and humiliation such an infirmity is wont to cause to those who groan under it, we may be inclined to believe that not the least probable hypothesis concerning the 'thorn' or 'stake' in the flesh is that the loving heart of the apostle bewailed as his sorest trial the misfortune that, by impatience in word, he had often wounded those for whom he would willingly have given his life" (Lias's Second Cor., Introd.).
6. A highly controversial theory has been proposed by Bishop Spong in his book Rescuing the Bible from Fundamentalism (ISBN 0-06-067518-7) which suggests that it refers to homosexual desires. Paul strongly condemned acting on such desires in his other writings. (Romans 1:26-27, 1 Corinthians 6:9, and 1 Timothy 1:10)
7. A meaning accepted by many Christians was that Paul had a person in his life that annoyed him. Paul would then sin (in what way is unknown, probably acting out in anger). This would show him he is man and fallible, still in need of Christ. It kept him from becoming prideful from his many glorious experiences.
8. Another view is that the thorn in the flesh refers to the inability Paul had to share the Gospel with his own people the Jews.

- Wikipedia