IT IS NOT WITHOUT SIGNIFICANCE that the real saints of history, as distinguished from morbid, self-flagellating ascetics, have a delightful sense of humor, as had Francis of Assisi, for instance. This sense of humor is based upon a curious quality of disillusionment which has not resulted in either bitterness or despair. It is without bitterness, because judgments of the fellow man are tempered by the forgiveness which is prompted by repentance. It is without despair, because no evils in the world can disturb the firm faith in the goodness of God and his ultimate triumph over evil. This quality of mirthful serenity is unlike the innocency of childhood which knows no evil. It has looked into the abyss of evil and is no longer affrighted by it.
— Reinhold Niebuhr
From his collection of essays Beyond Tragedy: Essays on the Christian Interpretation of History.
I do like "mirthful serenity." Yes I do.