It's good you separate these issues of how or how not to live a mortal life. One aspect of this is the question "why is life so desirable and precious to us?" We take that as a given. One answer is "because we're genetically programmed to think death is bad."

Our genetic programming doesn't make things good or bad from an existentialist perspective. We're free to not listen to our fear of death. It's a choice any one of can make.

The benefit of this choice is it allows for. more focus on finding a fulfilling life (if you want one, not that you have to) whatever that fulfillment is, beyond simply fulfilling one's genetic programming.