We all do it, we are our own biggest critics. No matter what we do, we think I should have done it better. Knitters and Makers are especially guilty of this. We look over every stitch and wonder why it isn't perfect. Let me tell you why it isn't perfect, its HANDMADE, by a HUMAN, not a machine. Perfect isn't possible. Stop trying to achieve it, you can't, you won't and you're just enjoying the process less.
I was guilty. I'd make a mistake and couldn't stop fussing over it. I'd either rip out a project and start over or just abandon the project completely. My friend Chase of The Black Squirrel, challenged me on perfection and helped me break the habit. I declared my first Find your Fade Shawl to be my practice in imperfection. Every so often the count would be off in the lace work. I would just repeat Chase's words in my head "That shit will block out". There are loads of errors throughout the shawl but guess what? I continually get compliments on the finished shawl and NO ONE can see the mistakes. I'm declaring them "newly discovered stitches" from now on.
Next time you discover a new stitch, take a deep breath, and make a decision. Figure out if you can make a quick fix to make it work (Tim Gunn it) and move on. If it's something you absolutely can't live with, rip it back and do it again. Nothing is forever in knitting you can always just reknit the dang thing. Enjoy the process and give yourself a break.