The fear of death is a common one, and it's something that we all - even the bravest, most selfless souls - have to live with. It's that fear of not living long enough to see something, someone, somewhere, and to miss out. Or, it could be the fear of what happens after you die - not necessarily in the underworld - but perhaps to your loved ones in the living.
I've come to live with the fact that, as you've said, nothing is forever, and death cometh soon or late. Live life the best you can, and enjoy its bounties while we're still breathing. Do whatever you want, and have no fear. When death comes, you can stare it straight in the face, and say: "I've got nothing to lose"!
Very wise words to which I have to agree. I mostly worry about not seeing the people I love around me anymore. Those are the thoughts that cause me to lost sleep, although it doesn't happen as often as it used to when I was a child. I guess I a more sensitive to these things than other people as when I talked to my brother about this, he said he doesn't think about it very much. 😄
We all have our fears and anxieties, trivia or otherwise. It's nothing to be ashamed of, and facing it means that you can learn to overcome those fears, or simply learn to worry not about it 🙃.