Does it ever get any easier to let go?

I have been involved with a narcissist for a little over a year. This man has made my life hell for over half of that time and yet every time I feel strong enough to let go he reels me back in.
I know he will never change and can be extremely emotionally abusive when not getting his way. He expects my life to revolve around him and gives nothing in return except constant hurt. It's to the point I can do nothing on my own because it interferes with his needs.
He has cheated and still manages to try to justify it. Tells me all he time if I'm not willing to be everything he needs someone else will. Of course he is very attractive and charming at first. Every time we split up he gets on dating sites and has no trouble finding dates.
The past couple of months I have become stronger and gone no contact for longer periods each time, but keep falling back into it. My mind tells me that this is all so wrong and I deserve better, but it's almost to the point I feel like I am fighting for validation from him! And I know that's crazy and ill never get it, so why am I still letting him tear me apart emotionally? He has no regret for anything he has done to me, has never said sorry or anything.
He wanted to spend time together last week and I refused as I have been distancing myself...well he went out with someone he met online on Friday and they are spending a lot of time together and he is telling me he already loves her after less than a week. That is how sick he is, but it is breaking my heart that I sacrificed so much the past year and he is already settling down again. Although I know he will repeat the pattern and treat her the same it's still breaking my heart!
How do I let go and make my heart listen to my brain? I am feeling so hurt and devastated right now...