Eternal Sunshine of the Spotless Mind
What I love about this movie is how Clementines hair colors seem to correspond to the passion she feels for Joel. It's a subtle detail but if you pay attention to her hair color, you see how it relates to her relationship with Joel. One scene it was green-envy, then red-passion and lust, and then Blue-sad.
You also learn that one danger of intimacy is that we learn the other's vulnerabilities, we learn what buttons to push, and what not to push.
My favorite quotes-
Clementine: You know me, I'm impulsive.
Joel: That's what I love about you.
Joel: Why do I fall in love with every woman I see who shows me the least bit of attention?
Clementine: Too many guys think I'm a concept, or I complete them, or I'm gonna make them alive. But I'm just a fucked-up girl who's lookin' for my own peace of mind; don't assign me yours.