I realize regularly that I deal with existential dread, but not simply out of a fear of death. I'm not afraid of dying, per se. If I woke up tomorrow morning with a mad fascist and a gun to my head, I'd probably laugh.
It's not death I'm afraid of, it's approaching death. It's getting old, and older, and things continuing to be the same — or worse. It's lying there, incapable, knowing I can do nothing and will do nothing and quite possibly never have done anything of consequence to make them better.