I get the same way sometimes but I've gotten pretty good at just shrugging and saying to myself, "Lesson for next time!" and moving on. I rip out some mistakes but I leave a lot of them too. Some day I hope I'm as skilled as my grandmother, who deliberately added mistakes to her quilts! For now, plenty of them happen all on their own, LOL. And most of them wouldn't be noticed by a non-quilter anyway. I don't make show quilts (yet) - mine are designed to be portable hugs, and who will complain if a hug is not perfect!? It's the love that counts.