Think often of how swiftly all things pass away and are no more - the works of Nature and the works of man. The substance of the Universe, matter, is like unto a river that flows on forever. All things are not only in a constant state of change, but they are the cause of constant and infinite change in other things. Upon a narrow ledge thou standouts! Behind thee, the bottomless abyss of the Past! In front of thee, the Future that will swallow up all things that are now. Over what things, then, in this present life wilt thou, O foolish man, be disquieted or exalted - making thyself wretched; seeing that they can vex thee only for a time - a brief, brief time!