How to stop dredging up the past?

Please, help! I’m stuck in the memories of the person I left months ago!!! It’s destroying me!

It was my decision to leave, though it was really hard emotionally. She was a psycho, my days with her were miserable. I’ve never had such a terrible relationship experience in my life! She was always detached and cold with me intimately, and at the same time she obsessed over who I communicated with. At work, she had to know about all my female colleagues in detail, while raging about any contacts outside work.. When I tried to reason about my own needs, she always appeared to be on the verge of tears and made me feel monstrous and conflicted at the same time. I realized I spent my energy and money on her, and all the while I was neglecting myself and my sanity. My friends helped me understand that I can not fix what refuses to be normal. I left and spent the first few weeks mad from my freedom!

But the memories of her creep back! We were together for four years. I had an engagement ring for her, it’s still somewhere in my boxes. I remember how sweet she was at times, and how often she said she loved me. I hated her unbearable control and treatment of me back then, but now I remember her words about how fragile she was and that she’d cared about small things to make me comfortable when I was ill. A few days ago I saw a dress on a girl exactly like she used to wear, and I caught myself almost texting her “how are you”. She called me cruel, and at times I wonder if maybe I was cruel, unintentionally? Why do I miss her? Why do I blame myself now? I’ve never wanted to be a father to my girlfriend! I hate how much it hurts more as time goes on…. Is it because her control over me was deeper than I imagined? Or because I left while maybe I should have forced that decision on her?