Meditations, Book 6, Section 14

Marcus Aurelius — The Emperor

Some things rush into existence, and others rush toward their end. Even what exists right now is partly gone already. Constant change keeps the world fresh, just as time itself makes the infinite age of the world seem always new. In this flow of all things, why should anyone care about things that pass so quickly? There is nothing you can hold onto. It would be like getting attached to a sparrow that flies by - you see it, then it's gone.

Don't think of your life any differently. It's just the breathing in and breathing out of blood, like ordinary breathing of air. What we normally think of as breathing in air and breathing it out each day - that's all life is. At some point you breathe out all your life into the common air. You only breathed it in recently anyway - yesterday, today - and with that breath came life itself.

Marcus Aurelius — The Emperor Original

Some things hasten to be, and others to be no more. And even whatsoever now is, some part thereof hath already perished. Perpetual fluxes and alterations renew the world, as the perpetual course of time doth make the age of the world (of itself infinite) to appear always fresh and new. In such a flux and course of all things, what of these things that hasten so fast away should any man regard, since among all there is not any that a man may fasten and fix upon? as if a man would settle his affection upon some ordinary sparrow living by him, who is no sooner seen, than out of sight. For we must not think otherwise of our lives, than as a mere exhalation of blood, or of an ordinary respiration of air. For what in our common apprehension is, to breathe in the air and to breathe it out again, which we do daily: so much is it and no more, at once to breathe out all thy respirative faculty into that common air from whence but lately (as being but from yesterday, and to-day), thou didst first breathe it in, and with it, life.