There is an interesting final note from Paul. He brings attention to the fact that he writes the salutation and closing remarks by his own hand. The body of the texts were dictated to a companion, usually Timothy or Silvanus or Epaphroditus. He wrote the beginning and the ending in his own handwriting as a token of his love for the recipients (2 Thessalonians 3:17).
This is one of the reasons many scholars believe Paul had problems with his eyes. In his letter to the Galatians, he feels so strongly about a warning that he writes a note in the middle of his letter, "See with what large letters I am writing to you with my own hand" (Galatians 6:11). He also tells the Galatians "you know it was because of physical infirmity that I preached the Gospel to you" (Galatians 4:13-14). He writes to the Corinthians that God would not remove the "thorn in his flesh" to protect him against arrogance (2 Corinthians 12:10-17).
We know Paul suffered torture several times in his missionary trips (2 Corinthians 3:23-29. Suffering is not an indication of lack of faith, or distance from God. Jesus suffered throughout his life, not just at the cross (Isaiah 53). Suffering reminds us that we're not home yet.
