New development Me standing up for myself

Sucks that once i did it, i have to keep doing, but on a lesser level - more like making sure i get my boundaries respected early from the beginning and then maintenance as need right? How bout i just dont let anyone get that close that i would need to place boundaries, this sound like the best way, at least right now. I didnt back down last night and it didnt go over well. 16 years together of me being passive and trusting. Then i stand up to lies aaaaaaaaaaaaand... i got put in a head lock and thrown on the ground. Knocked on the side if the head, and then not sure what happened after that.
Now i got to tell him he has to leave and it wont turn out great im pretty sure