Once you let someone start treating you lesser they get it in there head that that's the new normal.

Example: oh I raged at him and he just took it.

Then they think next time they can rage at you because you will just accept it and take it and then it's the "new normal".

She/he will flip out on you again and when u do react they are all taken aback and offended that your fed up and turn you into the asshole because your mad and fed up.