Optimism is the parent of despair, while pessimism allows the mind to accustom itself to the inevitable disappointments of human existence by degrees, just as some drugs induce a state of tolerance. Pessimists, moreover, have the better sense of humour, for they have a livelier apprehension of pretension and absurdity. In a meritocracy, furthermore, those who fail must either indulge in elaborate mental contortions to disguise reality from themselves or sink into a deep melancholy.

British Medical Journal Views and Reviews: Desperate house calls (BMJ 2009;338:b212).