You had an accident, and your confidence is hurt. Unfortunately that's quite a natural reaction, at least from what I've saw. I don't know about you, but I keep my acetone in a plastic bottle. I knew it degraded plastics, but who would have guessed it would melt a printer?
Sometimes it seems like we are expected to know everything. Try not to pressure yourself so much. It's okay to make mistakes. Try not to ruminate on what you could have done. You can't change the past.