Marcus Aurelius
Author: Marcus Aurelius
Publisher: Penguin Great Ideas (2005)

Above all, never struggle or strain; but be master of yourself, and view life as a man, as a human being, as a citizen, and as a mortal.  Among the truths you will do well to contemplate most frequently are these two: first, that things can never touch the soul, but stand inert outside it, so that disquiet can arise only from fancies within; and secondly, that all visible objects change in a moment, and will be no more.  Think of the countless changes in which you yourself have had a part.  The whole universe is change, and life itself is but what you deem it.