My favorites:
"This too shall pass." dunno who said it.
"Tomorrow and tomorrow and tomorrow creeps in this petty pace from day to day to the last syllable of recorded time. And all our yesterdays have led the way to dusty death. Out! Out brief candle. Life's but a walking shadow. A poor player who struts and frets his hour upon the stage and then is heard no more. It is a tale told by an idiot, full of sound and fury, signifying nothing." - Macbeth, of Shakespeare's play of the same name.
"Say what you will about the sweet miracle of unquestioning faith, I consider a capacity for it terrifying and absolutely vile." - Kurt Vonnegut
"I would love to believe that when I die I will live again, that some thinking, feeling, remembering part of me will continue. But much as I want to believe that, and despite the ancient and worldwide cultural traditions that assert an afterlife, I know of nothing to suggest that it is more than wishful thinking. The world is so exquisite with so much love and moral depth, that there is no reason to deceive ourselves with pretty stories for which there's little good evidence. Far better it seems to me, in our vulnerability, is to look death in the eye and to be grateful every day for the brief but magnificent opportunity that life provides. " - Carl Sagan