why do we stay?

For the first time in my life I was physically attacked by my partner. He swore it’d never happen again, swore he loved me, apologized to me after I said that does nothing for me it’s to help ease his mind. I love him so much, he’s never acted this way with me. I want to stay and live everything we once dreamed of but I see my bruised face and it’s hard to. I was already dealing with physical appearance insecurities because I am 9 months pp and also going through ppd. Besides my bruised face my heart physically aches, in a way I’ve never known before. So why does a woman stay?