Life is the ability to do things*. Much of my hatred of death is that it takes away ones ability to do anything and affect anything in the world.
To my chagrin, that is not the only thing that takes away one's ability to do things.
Last year I suffered a back injury. I'm slowly recovering, but it's altered my life. On the most easily-quantifiable level, I spend about an hour every day on physical therapy. That's a large chunk of my ~19 waking hours per day. I've lost over 5% of my ability to do anything else in a day to that factor alone.
My sleep is usually worse, so even in my regular waking hours I'm less productive. But much worse than that is the constant physical pain. It's been lessening lately, but it is a constant drain on my energy. I used to be able to Do Things for 15+ hours a day, if I needed to. Now I have a hard time just putting in my 8 hours/day for paid work, and I certainly get less done in those 8 hours than I used to. When I'm done with that work, it's not just that I don't want to go write a story, or improve my home. It's that I do not have the energy to do much of anything, because the relentless pain has sapped me of everything. It's all I can do to lay down and read for a while. Maybe I can get in an hour of other work in the evening. More likely I'll be putting it off to the weekend, where I won't be working as much as I used to at all.
At this point I'm up to maybe 2/3rds the ability to do things that I was at before my injury. This means it takes me 3 weeks to accomplish what I used to be able to do in 2 weeks, and it takes more effort. More strikingly, that means it takes me 3 years to accomplish what I once could have accomplished in 2 years. Assuming that I have another 30 productive years in front of me, if things don't improve further, that means it'll take me all those 30 years to do what before it would have only taken me 20 years to do. A pre-injury equivalent of 20 years of life is going to take 30 years instead. I will lose everything that I could have done in those hypothetical last 10 years that I won't ever get to now.
In effect, this injury has taken 1/3rd of the rest of my life, even assuming I live just as long as I would have otherwise. (and assuming I don't continue to recover). I haven't been killed... but 1/3rd of me has.
And it occurs to me, that this will happen more and more often as I age and my shitty meat-suit decays around me. There will be more injuries and insults that further degrade my capacity. That is what aging is. It's dying in pieces.
*Not a biological definition.
(On a related note, I always thought it was dumb when people said "Teenagers think they're immortal." No teenager I ever knew thought that, and neither did I. We knew we could die, and we feared it. What I think people meant (and should have said) is that teenagers don't realize you can die in pieces. I thought it was a binary thing, and either I would survive and (at worst) return to baseline after a few months of healing, or I would die completley. I didn't yet know that I had a middle-ground to be scared of, a dying that is partial, but just as permanent.)