I take comfort from the Good Book. And by that, I mean Vonnegut’s Slaughterhouse Five. The Tralfamadorean take is comforting. My conscious experience may its reach endpoint, but my existence will still have been, so to speak, embedded in the mountain range of time. The calypsos of Bokononism in Cat’s Cradle are good, too. Think of all the mud that didn’t even get to sit up and look around.
Furthermore, there’s a parable about the mountain, the one that a little bird comes along once every 100 years and scrapes its beak upon. When that mountain is worn away, only the first instant of eternity will have passed. Do we ever stop to think about what it would actually mean to exist forever? If it were infinite life, then once you’ve done everything that you enjoy for the billionth time and gotten so thoroughly bored of it, hey, you still have infinite time to go! After the Sun goes supernova and consumes the Earth, what will you do while floating in space for a few trillion years? If it’s existence after death, then a century or so of life will be as nothing compared to the vast sweep of eternity in the afterlife. Any number divided by infinity, and all.
Honestly, I figure that the urge to “live forever” is in actuality a desire to put off the existential crises to an indefinite time in the future. Cosmic procrastination. But living literally forever has its own (probably worse) existential horror. Everything has to end, especially in a universe that will end or at least cease being interesting, and that’s the only way that life can have any meaning.
The existential crisis comes no matter how long the Fates trim your strand, eventually you stare down the end. It’s just the price of admission.