2 Corinthians 12:6-7

Even if I wanted to boast, I would not be a fool, because I would be speaking the truth. But I refrain, so no one will credit me with more than he sees in me or hears from me, or because of these surpassingly great revelations. So to keep me from becoming conceited, I was given a thorn in my flesh, a messenger of Satan, to torment me.