back again....sadly

I was here last year, read alot, learned alot...but not enough.
Went back to him, believed the lies, was hopeful but...you guessed it...more of the same shit!
This man put me through hell last year. I went into a deep depression after I left him because he immediately started a new relationship hours (literally) after I left him and I was left stunned!!! At that time I did not know about narcissism and couldnt wrap my head around what was happening. I stumbled upon this site when I was trying to figure out what was happening to me and why it happened.
I felt relieved when I started learning about narcissism and I was doing ok but as soon as I spoke to him again, my brain went out the window and I got sucked back in.
So for months now I have been going through a roller coaster with him (again). Trying so hard to fix what I thought was wrong last time but with the same results. Lies. Cheating. Using. Ow. It never ends!!!
How do I end this? How do I stop the feelings of wanting to kill him over what he has PURPOSELY done? How do I let go of him once and for all? How do I get over the feelings of wanting revenge? HOW?????
Im so angry, at him and myself!!!
Because deep in my heart I knew, I was just hoping....
I really dont want to fall apart again like I did last year...not eating, not sleeping, depressed, etc.
I did the whole anti-depressant thing and it didnt help. I did counseling and I felt like they just didnt get what I was saying...like they were looking at me like I was stupid for putting up with his shit (which I am but not what I needed to hear).
I just need help and the strength to let him go and get over this but I dont know how. I really loved him and it pisses me off that he is so decieving and has zero conscious but is just a user. I hate the fact that he never would admit it even when caught. I hate that I even care about him. I hate feeling like I will never forget him when that is what I want the most. I wish I could just forget all about him and move on once and for all!!!!!!!!!!!!!!