i'm definitely not the best person to give advice on this. if I can't finish something in a couple days tops I usually just abandon the piece entirely lol. I work so fast to avoid running into that problem, but I would never recommend anyone to draw at an unreasonably rapid pace and potentially hurt themselves. I think just loosening what your definition of finished is could help. Use the "I could do better" feeling and reframe it as "I could do better... next time." So you can finish up a piece without feeling like it has to be perfect as you'll be able to start a new one from scratch afterwards with your more developed skills
