Yes. Just writing it will help you process it. Sharing it with us can help you process it and make it less powerful. I still will advise don't send it.
I've written a number of letters since DB, and stuck them in a box. Really reduced the urge after I wrote them. I don't know if I will ever let her read any of them. I certainly know I'm not interested in sending any of them in the near future. After a bit of time, you'll be able to judge whether the letter was what you really wanted to say or helpful. Then decide.
Me: 50 W:43 S6, S3 M: 12 yrs. T: 17 M is bad & Not happy Bomb Mar '14 S 5 Feb '15 D Bomb 13 Apr '15 (but "no hurry") DB Coach May '15 Wants proceed on D Aug '15 Starting 1-on-1 negotiations Sept '15