Walk away, slowly (like you did), take a deep breath, get a drink of coffee, water -whatever you like, spend time on the board, enjoy some fresh air. Then go back and start again. It works like a charm most of the time. When you do go back, sew slowly. I find when I think I've done this (whatever) so often before I can go faster...NOT. I have to remind myself that perfection takes patience, time and practice. And no quilt is perfect, so relax, enjoy.