I once heard of a young teacher who had yet to learn the skill of reflective teaching. The teacher was overcome with pure frustration when a lesson did not go as planned. When asked reflective questions afterwards, they couldn't express what could have been better or even what went well. It was rather difficult to find ways to improve when they couldn't identify the source of the problem let alone name the strategies worth repeating.
I've had plenty of experiences with errors. In fact, I've had twenty-one years of them. Some have been easier to handle than others. Thankfully none have been catastrophic, but a few still bother me or even haunt me for that matter. Regardless, they've instigated growth and continue to do so.
Although some of the best changes in my practice have resulted from an innocent desire for betterment, others are a product of errors that I refused to repeat. I recognized and analyzed a mistake and searched out a better way. Errors are simply unavoidable and part of the process of becoming a better teacher, so as Routman advises, we'd best take credit and pleasure in them. Our students will be better off if we do.