Note 2 at 2 Cor. 5:13: Of course, Paul was not crazy, but some of his critics had no doubt accused him of this. After all, he was not acting "normally." He totally disregarded his own well being for the sake of the gospel. He had fought with beasts at Ephesus (1 Cor. 15:32), he had been stoned and left for dead, yet he rose up and went right back in to that same city (Acts 14:19-20).

It is strange how the world considers someone who is not putting "self" first as being crazy. But according to the teaching of Jesus (Mt. 10:39; 16:24-25), those who deny self and put God and others first are the only sane ones.

So, Paul wanted these Corinthians to know that whether they considered him sane or crazy, everything he had done was for their benefit.