From the March 3 TBC Apples of Gold calendar:
Regardless of what we might want the Scriptures to say, Paul very plainly says that he was "given...a thorn in the flesh" in order that he not fall into pride or be exalted above measure because of the abundance of the revelations. The loving God who created Paul knew every weakness of this man and what would be needed to keep him from falling prey to human pride. –TBC
"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."