Like I said, it takes practice. Write yourself a note, telling yourself to stop. Record a video talking to yourself about why thinking back about bad experiences is harmful. Everyone says or does dumb stuff. Some of us make more out of our own dumb stuff that anyone else makes of it. You would never needle someone else for their mistakes over and over again. Why do that same thing to yourself? You're going to have to find your own system for this, but with repetition, it will come easier. You'll find you interrupting these times when you are thinking back about bad experiences. Questions you can ask yourself... What am I gaining by spending thought on this? Am I really going to come up with any new insight? Anything new to learn here? Am I helping myself right now? Am I hurting myself right now? How much time have I spent thinking about this? How much more time will I spend thinking about this. Develop your own internal coach to help you focus. I hope something here clicks for you. Or that it helps you find something that clicks for you. You won't get there today or tomorrow. But you can start today. It's a skill and it will take time and practice.