There is a limit to the time assigned you, and if you don't use it to free yourself it will be gone and never return. (Hays translation) - Marcus Aurelius

He who does not know what the world is, does not know where he is. And he who does not know for what purpose the world exists, does not know who he is, nor what the world is. But he who has failed in any one of these things could not even say for what purpose he exists himself. What then dost thou think of him who [avoids or] seeks the praise of those who applaud, of men who know not either where they are or who they are?

The other reason is that what happens to the individual is a cause of well-being in what directs the world--of its well-being, its fulfillment, or its very existence, even. Because the whole is damaged if you cut away anything--anything at all--from its continuity and its coherence. Not only its parts, but its purposes. And that's what you're doing when you complain: hacking and destroying. (Hays translation)

If man reflects on the changes and transformations which follow one another like wave after wave and their rapidity, he will despise everything which is perishable.