I had to do stuff in baby steps. Partly because I was so scared to change, and partly because my living situation was getting to be more and more unsafe for me as I changed.
It's possible to change. It's possible to detach. It's hard sometimes, believe me. My ex got more frustrated and angrier as I made some positive changes, but I kept at it as i knew it was the right thing for me.
There were days I said the Serenity Prayer a hundred times. I started to set and work on some small boundaries. Like I said, baby steps.
Going to al Anon and working these steps saved my life. I say it all the time.