I've had some health issues come up recently of indeterminate nature and resolution that has had me thinking on this in recent months. However it's something i've dealt with personally for years, even before i was double digits in age. The terror of non-existence.
Getting around that steep mountain is up to you. The question is rather, what to do with the time that you have? Do you lay down and die, despairing of the heat death of the universe? Don't worry about that because in a mere five thousand years no one will remember who you were anyway.
True virtue is acting virtuously without the fear or threat of being observed. It's the, how do i live my life alone on a desert island until the day i die?, argument. If you are trapped, alone, with no one to watch over you, no one to judge you, what would you do? Burn the island down around you? Torture every animal at hand out of spite and sadistic impulses? Sit alone and watch the sunsets turn into night until the crickets turn our your lights? Or build, think, create and do; not because you are compelled by society to but because you can?
We're thinking apes with opposible thumbs - toolmaking apes - where the cognitive ability to hold a 'blueprint" or prototype tool is the fundamental cognitive breakthrough that allowed us to conquer the world. This is our nature, whether we like it or not. We're not space faring gas-grazers munching on helium in the orbits of Jupiter nor immortal but immobile rock-crystals bored from watching our slow impending doom from erosion and plate technonics. Is it braver to do good without hope of reward than one who throws themselves into the fire convinced there's a heavenly reward waiting on the other side?
Now think of how much all your ancestors have sacrificed to see you throw it all away. Think if your sons or daughters came to you and said "Dad, i'm bored of this life, what's the point of going on?" Did you work and strive and accomplish to see them say that?
Ours is a destiny of work, toil, love and joy, loss and gain, and to strive to add or own paving stone to the work of history. Think off all the unfortunates before us that never had the chance for such a choice, stolen from them whilst young by disease, accident, violence or ill fortune. There are universes out there waiting for you to discover; the one we live in and the ones we create inside our minds. Not finding a reason to keep going on seems like the only real mistake.