I tend to think of mistakes in a quilt as a "lesson for NEXT time", unless it's a real deal-breaker. If it's going to cause construction problems I'll fix things, but sometimes that "fix" is to just cheat and shave a bit off of the next block or to widen a seam elsewhere. I've been known to just go ahead and take up slack in a row by putting a pleat under a seam and stitching it down and calling it good...nobody has ever noticed! I like to quilt "by the seat of my pants" and just sort of wing it for a lot of my quilts. It's more fun for me that way and that's why I do this - because I enjoy it. And even with my slap-dash attitude, I do take care in my quilting and each quilt is that much better than the last.
Quilts I intend to show or enter into the fair are a little different - on those I go slower and try to follow at least most of the rules. But that's a small percentage of the quilts I'm making....most are just for fun.