Some tricks:
1) Write a list of your errors and then burn it.
2) Visualize all the regrets and bundle them up. The bundle will be huge. Envision setting it down and walking away from it. Each day picture in your head the bag sitting on the side of the road as you get farther and farther from it until eventually you turn in the road and go no longer see it.
3) Each time you find yourself thinking about it. Stop and redirect your thoughts. If you have to say: STOP outloud then do it. Have a plan of what you will think of: Something you like about yourself helps. Think of people who like you. They can't all have bad taste.
I share about my silly tricks often because they helped me a lot. I had no idea how negative I was towards myself until I started replacing the negative with the positive. It felt really silly at first but they have gotten me out of several bad spots in my life.