Look on the bright side

Remember when old December s darkness is everywhere about you, that the world is really in every minutest point as full of life as in the most joyous morning you ever lived through; that the sun is whanging down, and the waves dancing, and the gulls skimming down at the mouth of the Amazon, for instance, as freshly as in the first morning of creation; and the hour is just as fit as any hour that ever was for a new gospel of cheer to be preached. I am sure that one can, by merely thinking of these matters of fact, limit the power of one's evil moods over one's way of looking at the Kosmos.

William James, Letters I
To Thomas W. Ward. BERLIN, Jan., 1868.