Think of your many years of procrastination; how the gods have repeatedly granted you further periods of grace, of which you have taken no advantage. It is time now to realize the nature of the universe to which you belong, and of that controlling Power whose offspring you are; and to understand that your time has a limit set to it. Use it, then, to advance your enlightenment; or it will be gone, and never in your power again. (Meditations, book 2, paragraph 4)* Okay, so unlike the good emperor, I do not literally believe in any gods, nor a "controlling Power whose offspring [I am]". But it's no problem to set aside those bits, or read them metaphorically, while agreeing with the rest.
More from this ancient Stoic to come.
Photo of a bust of the young Marcus Aurelius, from the Wikimedia commons. Taken by Marie-Lan Nguyen and released into the public domain.