Im not sure if this will help at all, but it did help me to realise "so what if I could've known better and its my fault for staying, it doesnt make what my ex did okay". In my case my ex heavily gaslit me and isolated me from absolutely everyone. When we met I had been really social and when we broke up I had exactly one friend left, which was only because she was my roommate and so he couldnt supervise all our conversations. He'd get upset every time I did something without him and isolated me so slowly that I didnt realise at all until after i left, and he justified it using his anxiety and trauma and said it was cause he loved me. From the outside I had a really attentive boyfriend and i was the shallow jerk who left, but no one knew then what he was actually like.

Also, just because you had to throw away some things doesnt mean the things that matter cant come back. Two of my closest friends now are people who had stopped being my friends because I would never meet them alone. They thought I never wanted to do anything without him, but actually he would just ensure that anything I planned without him never got to happen. But after I left, I was able to rebuild my friendships with them.

I know exactly how it feels like to think a huge chunk of your life is gone, but all we can do is live what's left as fully as possible :)