Say it with me. Let it go, let it go, and guess what? Let it go.
One of our biggest problems is that we always dwell in the past. Just let it go, its already done. Thinking about it isnt going to change anything. The only thing thinking will do is WASTE your time, and bring back all those horrible FEELINGS you "think" you had when that moment was actually happening.
Waste our time you say? Yeah. You know how people always ask you if you are okay? If you are feeling sad? Etc, etc. Well thats because we are always lost in thought. Always thinking about the past, and always thinking about the future. We aren't actually PRESENT in the moment. Our bodies are there but our mind is off in a distant world. No presence. Something we all can work on.
So when you think of something and go "crap I wish.. this and that couldve gone better.." Well what can I say? What can you say? It already happened. Worry about the now, and the past wont be such a problem.
This person said something interesting. I highly recommend you all read it. d3lusionkt
Something i've been wanting to add to the OP.here
My opinion on how to improve ourselves.here