The thing is that..

Allie: You arrogant son of a bitch!
Noah: Would you just stay with me?
Allie: Stay with you? What for? Look at us, we're already fightin'
Noah: That's what we do, we fight... You tell me when I am being an arrogant son of a bitch and I tell you when you are a pain in the ass. Which you are, 99% of the time. I'm not afraid to hurt your feelings. You have like a 2 second rebound rate, then you're back doing the next pain-in-the-ass thing.
Allie: So what?
Noah: So it's not gonna be easy. It's gonna be really hard. We're gonna have to work at this every day, but I want to do that because I want you. I want all of you, for ever, you and me, every day.