That happens to me too, I just let it go, let it goo. jk
I either set it aside for a while and come back to fix it later, or I just let it go and try to not make the same mistake in the next art work I draw.
Because there's no reason crying over spilled milk. If you can't fix it, learn from it. A lot of my old work I can see a lot of mistakes, I can fix them now, but there's no reason to; especially when I can make new and better art. I keep my old art as a reminder that I was once a baby artist.
Your heading the right direction, but don't be too hard on yourself. One day you'll look back at those work and realize how much you have improved.