First:
You are dying. Let that in; dwell on it.
Being alive can be pretty amazing; the world, people, life… But the price of entry is that your time is limited, and will end. oh, and you have no idea when. :)
So “being alive” is, by definition, to be actively dying.
Second:
Anxiety (worry, dread, etc) is always and only ever based on an imagined future. This is where you are right now, imagining outcomes you have no way of knowing. Sadness (regret, self doubt, etc) is entirely focused on a remembered past. We all experience both.
Right now is all you really ever have. Learning to put (and keep) your attention there takes work, but it’s worth it!
"Security does not exist in nature, nor do the children of men as a whole experience it. Life either a daring adventure or nothing.”