I do like Sadiemae if it's not a glaring mistake, but I also leave very long "tails" of thread at the end of my mistake and the beginning of the sew over and then just bury them by hand when I'm done quilting. Actually, you're the only one that's going to know you made a mistake unless you point it out to them or it's really a "biggie" right smack dab in the middle of the quilt and you can't help but see it but there's usually always a way to cover it up. Don't agonize over it too much or it will take the fun out of quilting :)