Here are some quotes about letting go of the past that I found:

- "If you want to be happy, do not dwell in the past, do not worry about the future, focus on living fully in the present." - Roy T. Bennett
- "The truth is, unless you let go, unless you forgive yourself, unless you forgive the situation, unless you realize that the situation is over, you cannot move forward. When you let go, you move forward." - C.S. Lewis
- "Letting go means to come to the realization that some people are a part of your history, but not a part of your destiny." - Steve Maraboli

I hope these quotes help you in some way.