One of the recurring themes in the Bible is that people need help from God to do His will. Sarah received strength from God in her old age to conceive Isaac. Moses was given the power by God to perform miracles and stand before Pharaoh to lead Israel out of Egypt. There are numerous others. Paul was forced to rely upon God when he was given his "thorn in the flesh." When the Lord told him He would not remove this impediment, Paul learned to rely upon God's grace and the power of Christ in his life. He said that it was in his weakness that he became strong.