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. 2 Corinthians 12:9
The Apostle Paul had been beset by an affliction of some kind. He had been used of God to heal others, so much so that even when cloths taken from him were put on the sick, they were healed. He sought God three times for healing, but God gave him the grace to endure it instead.
Paul gives us insight into why he was afflicted:
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. 2 Corinthians 12:7
Paul understood that his affliction was so that he would not become prideful and God's power would be seen in him all the more.
Sometimes, God is more glorified by our shining for him in the midst of our suffering than by our healing. His grace shines through when we, appearing weak, wax strong in the calling he places on us. We are to live for his glory, not our comfort!