Jamieson, Fausset and Brown on 2 Corinthians 1:4

4. us--idiomatic for me (1Th 2:18).

that we may ... comfort them which are in any trouble--Translate, as the Greek is the same as before, "tribulation." The apostle lived, not to himself, but to the Church; so, whatever graces God conferred on him, he considered granted not for himself alone, but that he might have the greater ability to help others [Calvin]. So participation in all the afflictions of man peculiarly qualified Jesus to be man's comforter in all his various afflictions (Is 50:4-6; He 4:15).