I'm fascinated by how the replies in this thread split between "don't bother - no-one will notice, the quilt will still be loved, and no-one's perfect" and "do something about it because it'll drive you crazy if you don't fix it". Really reflects how different we all are in our ability to tolerate errors! I've moved from one to the other - when I started quilting I picked up that I was supposed to aim for perfection, and it often made me very miserable. Since then I've relaxed a lot more, and as long as I know that I've done my best, I can forgive myself my mistakes, and take the view that I learn from them.
But it would be a dull world if we were all the same!