For me, right now, it's mostly the fact that years of drug abuse and psych drugs have reduced my ability to feel pleasure. I've been somewhat depressed my whole life, but even then I always had the ability to enjoy music or sex or chilling with friends and actively sought those things out. Now nothing packs quite the same punch, and I do not see the point in making an effort to work away at something for little mental reward. There's a quote from Bojack Horseman that comes to mind, something along the lines of "I keep turning over the nothing to find something, but all there is more nothing, and then I turn over that nothing but there's just nothing".
Something in my brain changed after I quit drugs, and my life got shittier. I wish sometimes that I never started using drugs to cope, or that I didn't stop using. The shit I worried and felt depressed about as a teenager seems trivial compared to this.
I don't know, it seems like there's always gonna be something shitty happening and that'll take over everything else no matter how hard I try to stay positive or work on it in therapy.
I don't want to die, I just don't want to live with my mind and the way it works most of the time. I've tried to change the way I think , but it didn't change how the bad always outweighs the good infinitely. I kind of just want to go back to living in the moment (using drugs again), impulsively and dangerously, until it stops being fun and then just opt out of living. There's just nothing really worth living for that I've found so far (except drugs lol), and I don't want to spend my whole life looking for this thing that probably doesn't exist.
TLDR: quality of life has been compromised by anhedonia and long standing depression. Really don't want to deal with both
Sorry for rambling, you can reply if you want to.