Any tips on leaving?

I’m preparing to leave my husband for various reasons. It’s going to be one of the hardest things I’ve ever done as we were high school sweethearts. He just treats me like dirt. How do make this go as smoothly as possible and make it a good transition (or as good as possible)? How do I move on and not dwell in our life and what it could have been? I can’t see myself with anyone else but I’ve got to love myself enough to get out. I’m just struggling on how to make this all happen. If I can just get out and get settled in somewhere else and get all the bills split up and squared away i would feel better. Any advice? I’m planning to leave after Christmas.