Hi, try to hang in there. It’s extremely hard and despite what he did to you, it’s normal to feel empty and miss him. This is why so many women go back time and time again as it feels like the only way to heal that empty gaping hole in your heart is him. Nobody can prepare you for the emotions you feel after leaving, as well as the issues you have to sort out with finances, kids if you have any together and housing. These feelings will lessen as time goes on and it will be worth it.
I think perhaps what you are pining for is the good times, the dream, the person you thought he was. It is like a grief process many of us experience. Cry all day if you feel like it, post your heart away on here as we are here for you but fight the temptation to go back to him. Remember why you left him and keep reminding yourself, write it down and look at it when you have weak moments. I find that helped me.