Letting go of something you know is bad for you

Its so hard. My partner is horrible to me. He's hit me a few times and always puts me down then he says it didn't happen, so he's gaslighting me and he's manipulative and abusive. But the good times are so good it makes it so hard to walk away and It feels like I can't manage without him. But he makes no effort like he used to, I've said some horrible things to him and I feel so guilty and sorry I wish I could erase some things I've said. I know it's toxic and I said those things while I was hurting which is no excuse but I felt cornered and lashed out after him treating me like shit all this time. But there's something there that makes me want him so much and I can't leave