Good question. It's all down to temperament, isn't it? For some people, producing work that's as neat and accurate as possible is part of the pleasure and the challenge. For others that just doesn't matter so much. I'm the latter but for quite a while tried to be the former - and nearly gave up quilting, I was so miserable when I got things wrong. Light eventually dawned thanks to seeing an exhibition of antique quilts at a museum. Some of them had quite glaring errors, yet there they were on the gallery walls, admired and honoured by all who saw them. Nowadays "good enough" is enough for me. I would undo very obvious errors, as they'd continue to annoy me, and I'm careful where lack of accuracy would just cause problems -eg with cutting out and seam allowances - but am relaxed about minor imperfections. I'm more fussy if I'm making a quilt for someone else, because I want to do my best for them, but I still wouldn't stress if something was't quite right, as long as I'd done the best I could.
A friend saw the quilt I was finishing this week and asked if she could buy it for her daughter. It was one I'd only made for myself, and a few things had gone wrong - including (shock horror!) a patch on the backing because in one corner it hadn't covered the batting and I didn't see it till I'd started quilting. I carefully pointed out the errors. Her response? - that's all part of its hand-made charm! Non-quilters don't always share our concerns for the detail - they see the whole and see something beautiful, where we often only see the mistakes. (And that probably applies to our lives more generally).