On the Shortness of Life, Section 15

Seneca — The Senator

This is the only way to extend your mortal life — or even make it immortal. High positions, monuments, everything that ambition records in laws or builds in stone — all of it crumbles quickly. Time destroys everything. But the things that philosophy has blessed cannot be harmed. No age will throw them away or weaken them. Each century that passes will honor them even more. We tend to be jealous of what's close to us, but we admire distant things with clearer eyes. So the wise person's life includes much more than others. He isn't trapped by the same limits that confine everyone else. He alone is free from the laws that rule mankind. All ages serve him like a god. If time has passed, he recalls it through memory. If time is present, he uses it. If time is future, he looks forward to it. His life is long because he gathers all times into it.

Seneca — The Senator Original

By this means alone can you prolong your mortal life, nay, even turn it into an immortal one. High office, monuments, all that ambition records in decrees or piles up in stone, soon passes away: lapse of time casts down and ruins everything; but those things on which Philosophy has set its seal are beyond the reach of injury: no age will discard them or lessen their force, each succeeding century will add somewhat to the respect in which they are held: for we look upon what is near us with jealous eyes, but we admire what is further off with less prejudice. The wise man's life, therefore, includes much: he is not hedged in by the same limits which confine others: he alone is exempt from the laws by which mankind is governed: all ages serve him like a god. If any time be past, he recals it by his memory; if it be present, he uses it; if it be future, he anticipates it: his life is a long one because he concentrates all times into it.