If you are much troubled, more than average, by the thought that life will end, I want to see if I can say anything that might be useful to you.
Maybe the first thing to say is that you are not alone. We are people, but people are animals, life forms, and our bodies are vehicles for the force we call a human life.
Because we are alive, we are naturally death-averse; most of us most of the time try to avoid death, the only exceptions being desperately unhappy and self-destructive people. Even people who seek out dangerous activities don't actually want to die doing them, they just want the thrill of getting close. Being death-averse is how a life preserves itself, whether it's a sea-slug or a duke. So it’s perfectly natural, at a biological level.
So being death-averse works at the level of instinct and action. But being aware of one's own mortality is a different matter. Antelope become particularly death-averse if they sense a cheetah stalking the herd, but they don't, we can be pretty sure, worry about the fact that one day their life will end.
It seems certain that human beings are the only creatures on the planet who know, in advance of the event, that their lives will end. This can be seen as a blessing (we can plan our lives, at least to some degree, and value them because we know they’re limited) or a curse (most of us fear death) or most likely a mix of both.
In any case, we have to live our lives with this knowledge, however we feel about it. It's not just that people die, which makes us aware that we are not immortal; it's also that knowledge of our mortality tends to make us strive against it rather than accept it. Particularly now, in our culture.
Did you ever see an illustrated book for children called "Hildilid's Night?" Hildilid lived "high in the hills above Hexham," and every night she tried to get the darkness of night out of her little house. She would try to sweep it out, wash it out, slam the door against it - in the end, in her frustration, "I'm sorry to say," wrote Cheli Duran Ryan, she spat at it.
The night, of course, was unmoved. It stayed dark until the dawn. That is what nights do. But by the dawn, Hildilid was so exhausted by her futile struggle that she fell asleep, and slumbered right through the day until - nightfall, when once again, she battled in vain against the night....
Poor Hildilid. We're all Hildilids to some extent, because it's natural to be wary of the dark, if not to fear it. It's natural to have some fear of death, but it makes life difficult if we are Hildilids about our mortality, tiring ourselves out by fighting something that can’t be fought, instead of simply living our lives.
I’ll return to this business of our mortality (by which I mean the fact that life ends.) But a thought occurs to me: maybe what is really troubling you is loss, rather than the simple fact of mortality. That is, maybe it’s not death itself that’s troubling you, maybe it’s the thought that you might lose someone close to you. Big stuff, isn't it? I'll listen to the water and get back to you on that....