2 Corinthians 12

 Without giving us any more information, Paul states - 

"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.

8 For this thing I besought the Lord thrice, that it might depart from me.

9 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.

10 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 Corinthians 12:7–10)

I think most of us have a "thorn in the flesh" or weakness.  Paul reminds us, His grace is sufficient.