If someone hurt you and broke your heart, here is a simple template you can use to write a break up letter to someone who hurt you.
I have felt a lot of pain inside me ever since I experienced what you did to me. I know that we should all forgive and forget but this is one exception. What you did to me was really merciless and it will be a long time before I can recover from it. In fact, it is something that will only disappear from my mind if I completely forget about you.
You are not the only one at fault after everything has happened. I also blame myself as I expected so many things from you. Of course, my expectations were not met but that does mean you should change. I am sure you will find someone who will love you just the way you are. I just prefer to find other qualities in a partner.
I apologize for saying this but it is time to move on.