I make a hell of a lot of mistakes. Not sure if I said it here before, but I learned something from a legendary furniture maker early on. He told me that a good craftsman isn't perfect. He just knows how to recover from mistakes.
I make little ones and big ones. The minor mistakes are usually fixable. This would be something like attaching the wrong type of binding. I'll route it out and install a new one. It's a big pain in the butt, but less work than building from scratch again. Sometimes I might decide to add an inlay to cover a mistake.
Then, there's the big ones. I've smashed a couple instruments while buffing. It's the most depressing/angering/ego deflating/frustrating thing that can happen. Almost all of the work has been done on the instrument, then BOOM! If the cracks are bad, I build a new one. Most of the time, they're bad, if the buffer grabs the instrument.