Religion, children, and legacy are the ways people cope with this. For the vast, vast majority of human history, 99% of people believed either in an afterlife or reincarnation or something of the sort. Having children, who were molded in your image and expected to take over your life's work, doing the same work you did. Or otherwise leaving an impact in the world, hoping that your legacy would be remembered and to pass on your teachings and experiences to future generations even if not to your own children.

I think advances in scientific understanding may have unfortunately been detrimental to mental wellbeing at scale. Knowing that there is no higher power or grand purpose, knowing that our civilization is probably cooked in the near term, and knowing that even if our civilization isn't immediately cooked, Earth and eventually the universe is, are all not greatly emotionally satisfying.

It probably doesn't help that every scientific advance gets co-opted to make the rich richer and civilization worse.

I guess the world oscillates between good times and bad times. Those who are born in bad times get to see the world improve drastically and babe purpose. Those who are unlucky enough to be born in good times get to see everything crumble.