This useful little reminder of transitionality has a number of variants and related phrases, including "memento mori" and "this too shall pass". Among these, one originates in A Canticle for Leibowitz - the lauded post-apocalyptic novel that also brought us "Flame Deluge" - and far outshines its fellows in impact:

Sic transit mundus.
So passes the world.

Bleak. Final. Unarguable.
Lacking even the small hope inherent in the original.
The first on my list of things to shout from the rooftops when nuclear war comes.