The "thorn in the flesh" Paul is talking about was a physical infirmity not sin he could not stop doing.
Read 2 Corinthians chapter 12 all the way through.
In the very last verse look at what Paul says.
2 Corinthians 12:21 And lest, when I come again, my God will humble me among you, and that I shall bewail many which have sinned already, and have not repented of the uncleanness and fornication and lasciviousness which they have committed.
Saying that it is impossible for fornicators to repent and give up their vile sex practices is unbiblical.
1 Corinthians 10:13 There hath no temptation taken you but such as is common to man: but God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it.
Clever arguments to jusify sin either in oneself or others is not love.
Remember Job suffering in the flesh? That was from Satan.
Job 2:3 And the LORD said unto Satan, Hast thou considered my servant Job, that there is none like him in the earth, a perfect and an upright man, one that feareth God, and escheweth evil? and still he holdeth fast his integrity, although thou movedst me against him, to destroy him without cause.
Job 2:4 And Satan answered the LORD, and said,
Skin for skin, yea, all that a man hath will he give for his life.
Job 2:5
But put forth thine hand now, and touch his bone and his flesh, and he will curse thee to thy face.
Job 2:6 And the LORD said unto Satan, Behold, he is in thine hand; but save his life.
Job 2:7
So went Satan forth from the presence of the LORD, and smote Job with sore boils from the sole of his foot unto his crown.
It is obvious by reading 1 Corinthians 10:13 that it was not sin that God refused to take away but a physical infirmity that Paul was suffering through.
Many Scholars believe it may have been Paul's poor eye sight that he was praying about.
Galatians 4:13
Ye know how through infirmity of the flesh I preached the gospel unto you at the first.
Galatians 4:14 And my temptation which was in my flesh ye despised not, nor rejected; but received me as an angel of God, even as Christ Jesus.
Galatians 4:15 Where is then the blessedness ye spake of?
for I bear you record, that, if it had been possible, ye would have plucked out your own eyes, and have given them to me.
If Paul had a sin he could not repent of he was being a hypocrite by writing this to the Corinthians in the same chapter.
2 Corinthians 12:21 And lest, when I come again, my God will humble me among you, and
that I shall bewail many which have sinned already, and have not repented of the uncleanness and fornication and lasciviousness which they have committed.
I rest my case...