As so often happens, when someone is pushed back by unfair questions and accusations, their response is to tell their story: they may come out with reasons as to how things are or their life story or, as in Paul's case, write more personally. So, we are very fortunate that Paul was pushed! He writes about a huge vision that he had 14 years ago, which reminds the reader of how spiritually mature Paul now is! We read elsewhere- Galatians 1 v 15-18- that Paul spent three years in Arabia immediately after his conversion and it may have been there when he experienced this vision.
The other information which is squeezed out of Paul by his opponents' slander is that he had a 'thorn in the flesh', which became a chronic condition. Paul prayed to be released from it, but God told him 'No' and told him that it would keep Paul humble. We don't know what this issue was- it could have been recurring malaria or an eye condition possibly brought about through his meeting with Jesus on the Damascus Road, where he was blinded. In his letter to the Galatians, Paul states that the believers there would have plucked out their eyes and given them to him if that could have helped! (4 v 15) Note that elsewhere we are told that Paul dictated his letters for a scribe to write and that when he authenticates them by writing a few words, the letters are very large-Galatians 6 v 11. Both Tertullian (born 155 AD) and Jerome (born 342 AD) believed that Paul suffered from severe headaches
We also know that his recurring medical complaint meant that Luke accompanied him on much of his journeying. A great good fortune for us as Luke recorded Paul's travels in the book of Acts.
What is a challenging truth for the believer is that Paul was one of many examples of godly men and women who lived with chronic health issues which God did not heal. This is the man who restored Eutychus, to life and health who fell out of a window whilst listening to Paul preach (Acts 20 v 7-12)! It reminds us that healing is not automatic. I recall dear John Glanville telling me that, when he was first blind, well-meaning Christians would take him along to healing meetings, although he knew that he was not going to see again. I'm sure that many of the contemporaries of Paul would have laid hands on him for healing, when he had been told by God that he was to have a lifelong condition. We have to spend time listening to God and also listening to the sufferer themselves, not automatically assume that God will bring healing.