Doesn't help that you talk yourself down at every given opportunity, but you haven't given up yet so you'll be fine.
Having been in that hole myself, i can confirm that it does bad things to your self-esteem. Sure, i still self deprecate nowadays, but mostly because it amuses me, not because i actually believe i'm a slow and lazy shit (well i am objectively lazy and absent minded, but that's not really something that bothers me). It just doesn't feel right to toot my own horn at every given opportunity. :v
But yeah, reiterating what GUNIN said, you gotta try to accept your creations for what they are at the time, accept the flaws they have, and try to learn from those flaws. I'm not gonna pretend that i love how everything i make turns out, i've had plenty of things where i thought like "this went terribly", and even one case where i just flat out deleted the entire thing because i hated it so much. It happens, it's fine. Try to figure out WHY you don't like the outcome, and don't you fucking dare say "because i suck". It's something about the drawing itself, and since you now have it before your very eyes, you can scrutinize it and figure out what went wrong. Then, you can either experiment and try to fix it on your own, or look up how other people do that thing, or some other thing i can't think of off the top of my head. I personally lean towards the former, but either way works. Just don't settle on "i don't like this" for everything, that won't get you anywhere.
Also, make sure to reward yourself by taking note of the things that went well. It can be rough to only look for all the bad things, because that might instill a belief that you only make bad things. That is rarely ever the case, and no you are not the rare exception.
I actually have a convenient example ready, even though it wasn't made for this purpose; i'm gonna spoiler it for size.
So there's the sketch. I'm fine with that, so i proceed.
It then struck me that i didn't like this outcome. But why? A bit of scrutinizing revealed that i specifically didn't like the beak and how the eyelid lines didn't converge. The beak isn't the one i originally drew the character with either, which probably didn't help, and many of the lines just don't flow well enough, so i engaged some nitpicking.
Lines smoothed out a bit in some places (mouth is now one sweep instead of three separate strokes, for one), beak fixed to look right, and the lines for the eyelids now follow the same curve. I'm now aware of these things, and can employ them in future renditions of this feathery fuck.
So tl;dr observe and identify. Actually fixing the drawing is optional, it'll work just as well to employ the knowledge in future works.