Then how come it is?

Ross: Okay, well here we are. Now we're in a tough spot again, Rach. What do you want to do? How do you want to handle it? Huh? Do you wanna fight for us? Or, do you wanna bail? Look, I, I did a terrible, stupid, stupid thing. Okay? And I'm sorry, I wish I could take it back, but I can't. I just can't see us throwing away something we know is so damn good. Rachel, I love you so much.
Rachel: No Ross!!! Don't! You can't just kiss me and think you're gonna make it all go away, okay? It doesn't work that way. It doesn't just make it better. Okay?
Ross: Okay, okay, okay.
Rachel: I think you should go.
Ross: What?
Rachel: I really think you need to go now.
Ross: Okay, okay. This morning you said there was nothing so big that we couldn't work past it together...
Rachel: Yeah, what the hell did I know!
Ross: Look, look, there's got to be a way we can work past this. Okay, I can't imagine, I can't imagine my life without you. Without, without these arms, and your face, and this heart. Your good heart Rach, and, and...
Rachel: No. I can't, you're a totally different person to me now. I used to think of you as somebody that would never, ever hurt me, ever. God, and now I just can't stop picturing with her, I can't, it doesn't matter what you say, or what you do, Ross. It's just changed, everything. Forever.
Ross: Yeah, but this can't be it, I mean.
Rachel: Then how come it is?