It depends on the project and my mood. Some things require real precision, others not so much. I want to keep my frustration level under control. If I know that even I won't see a mismatched seam or a cut off point on a big quilt, then I am letting that go - unless I don't. I know what will cause me problems when putting a project together, so will do my best to avoid trouble at that stage. That is my goal in teaching a friend - if I know it won't go together, I suggest she redo it - otherwise, up to her how perfect it needs to be.