Here are links to some articles, from PsychCentral's archives, on the subject of how to let go of a painful past, the first by our host Dr. John Grohol, Psy.D.:

Learning to Let Go of Past Hurts: 5 Ways to Move On

Letting Go of the Past: Why Memories Remain Painful Over Time

Healing Wounds of the Past | Adventures in Mind, Body, and Soul

How to Cope with Pain from the Past

A Simple Strategy to Let Go of Painful Thoughts and Feelings | Dialectical Behavior Therapy Understood

https://psychcentral.com/blog/7-ways-to-let-go/

I wish you well...