Man, I've been there. At this point I'm pretty sure that a period of absolute despair is simply a standard part of the art process. Like, crippling depression and self doubt are as much a necessary step as idea, sketches, revisions, etc. I sure can't make anything good without spending some time feeling like human garbage in the middle. You know, at that point where it's clear that what you're actually producing is not shaping up as good as what you initially vaguely envisioned at the beginning. Then after staring into the void of self-loathing for a while, I recover and push through, rinse and repeat.