Truthfully there is nothing you can do for her as Nef suggested. I personally tend to focus on more of negative aspects of my XW than I do what was positive which helps frame my way of thinking towards her. I think you want to let her go but in the end you still come back to the same thing when you are cycling. The fond memories, the love, etc. when my mind starts to head that way I think of all the nasty $hit she did which refocuses my mind.
I think writing letters like you did can be of value. Most people would say not to send something like that because it makes you look weak but it is your sitch and if you feel like you want to then I am not going to stand in your way. I would advise against it but again it is your choice.
I got unstuck by taking care of myself. Lifting weights, playing basketball, going out with friends, spending time with my Daughters, buying new clothes, reading, learning, growing.......that is where I placed my focus and over time I mentally started to make the shift. Taking care of yourself and your S is how you move forward. You also indicated you are kind of dating someone. Another way for you to move forward.
