I hope it is okay that I list 3:
"Happiness can be found, even in the darkest of times, if one only remembers to turn on the light." -Albus Dumbledore from Harry Potter
"Dark clouds may hang on me sometimes, But I'll work it out" -Dave Matthews Band (Dancing Nancies)
"All the world's a stage,
And all the men and women merely players:
They have their exits and their entrances;
And one man in his time plays many parts."
-Shakespeare (As You Like It)