Basically, If something went "wrong" in your past, think of how it went right. Make a list of all the good aspects, the lessons learned. You can not change a thing about the past except how you perceive it. When thoughts about how it went wrong kick in, and they will, immediately choose to think of the GOOD aspects each time you have the chance. Don't for a second go down the Path of Wrongs, it will just build momentum. Eventually your perception will change as you begin to automatically think about the good aspects of your past. Both are thoughts, both are true. You labeled them "good" or "bad", no one else. If you can't truly do anything to change them, you might as well pick the thoughts that make you feel BETTER. Because wtf not!?