I think you have to focus on the end result. I know you will have tried everything to get to this point, and nothing is changing so you know what you have to do if you want a better life. 
I’ve had to walk away from my DP of 9 years recently and it hurts like absolute hell. But I know that my life will be another 30-40 years of feeling not good enough, being disrespected, being abandoned whenever he was annoyed, and watching him kick stuff around in anger.
90% of the time he was lovely - we had so many laughs, wonderful holidays together and amazing sex, but the 10% was so utterly heartbreaking that I’ve had to give up the rest and it’s awful.
But I’m holding onto the idea that there’s someone better suited to me out there, and while I’m with XDP, I won’t find him.
I convince myself that if this relationship is indeed meant to be then maybe in the future when he’s grown the fuck up we will bump into each other and be able to start again.
It’s helped that he has let me go without drama or a fight. If he had tried to win be back, the addiction might have been too strong. So for once I’m grateful that he hasn’t made me feel loved and that he was happy to lose me, because its allowed me to let go.
He always said we were meant to be together but if that was true why would I end up crying so often?
Ask yourself if this was where you were meant to be for the rest of your life, why would you be so miserable?