Learn from your mistakes and move forward. That's what I try to do every year.
I've made questionable calls as a drive coach that I still think about. I'll never forget telling our 2014 drive team to go for another high goal shot when a low goal would have secured the match and turned the St. Louis regional rankings upside down (Link:
http://www.thebluealliance.com/match/2014mosl_qm80 Sorry 1658 & 2408) I've watched that match video more times than I'd like to admit.
As many have said, you get better through experience. FRC isn't easy. The fact that you are worried about what you did wrong is actually a great thing. It means you want to improve - now the trick is figuring out how to do that. Focusing on one or two things each year is a good way to start, depending on your team size. If you get a little better each year soon enough your team will be great.