Replace it with positive thoughts about what is coming up in your new life, so you have no time to play the pain records over. Play records that have pleasant feelings with them. Abolish your mental museum of horror records. When you have good feelings you smile. Often within 30 seconds.
Feelings also come in stereo with actions.
You can control your thoughts and then the associated feeling. You can also get any feeling you want by appropriate action or motion. If you have little confidence, straighten up the slouch, carry yourself confidently, and within 3 minutes you will feel more confident. Initially, you have to fake or force these actions such as smiling, but then the feeling catches up and you don't have to force it any more. It will become more natural as the feeling catches up.