How can I stop repeating scenarios in my mind to figure out what I could have done better?

Probably recognizing the fact that we cannot go back into that moment and change things but just remember what we would have done differently and apply it to a future situation.

The problem with this is simply understanding the situation that happened. If you keep replaying it in your mind it simply means you don't confidence in what you said. But the point to understand with this is everything happened for a reason. You chose to say what you said for a very specific reason and your mind, at the time, thought it was the best route at the time. It wasn't until after the situation happened that you thought of the other possible routes.

Have compassion for who you were back then. You did what you thought was best with the knowledge you had. If those scenarios didn't happen you would not be able to look back and see how much you have grown.

'Could-have-done-better' is PAST. But the past is already gone. Have a post-it, or a note written on a paper, and keep it handy to read it as often as possible. The note being - "No matter how many times I repeat scenarios, I cannot change the past. So let me, for once and all, take a learning from what all I could have done to make things better, and start/try to do all such possible things in the present, or even use the learning from them, to put as an input to my future endeavours" Keep Smiling :)

Accepting the fact that they've already happened and moving on. "God, grant me the serenity to accept the things I cannot change, The courage to change the things I can, And the wisdom to know the difference."

its a habit, and habits take around 3 weeks to break, so make a new habit, when you can feel yourelf doing it, do something else, go for a run, walk the dog, sing a song, take a shower. eventually you'll break the habit

You can stop repeating scenarios in your mind to figure out what you could have done better by telling a close friend how you truly feel. They will understand. I promise.

Keeping bogged up thoughts in your mind and trying to process them chronologically can be very challenging. A good solution to make sense of what you could have done better is to write out your thoughts :) like a diary. This will definitely help you have a clearer train of thought.

I don't think you can. The best thing to do is give that scenario closure. Just wait, try to forget it happened, and go on to a different chapter of your life. Things sort themselves out after a while, and more important things will happen in your life.

When this happens to me, I try to distract myself. Personally, I either work out, listen to music, cook, etc. It is important to acknowledge what we could have done "better" in situations, however, when we start obsessing about how we have messed up in the past, it prevents us from moving forward.