How do I move on?

I'm in a very toxic relationship with some emotional abuse, I think. I have a daughter with him. Some days I am so so unhappy and feel terrible about myself. But then we have good days and those are what keep me holding on...

I know I need to leave. I'm just so scared about missing him. How do I ever move on? How do I stop myself from going back to the comfort and familiarity of it all?