Brooke breaks up with Lucas, even though she still loves him, because she saw him kissing Peyton. Lucas is really hurt and can't stop thinking about Brooke.
It shows how Brooke was kinda tired of how things were turning for her and Lucas and she tells him she gotta go her own way but Lucas don't wanna give up on Brooke because he's still in love with her and he really regrets all the mistakes he made.
