How we cite our quotes: All quotations are from Eternal Sunshine of the Spotless Mind.
Quote #4
JOEL: I love being bathed in the sink; such a feeling of security.
CLEMENTINE: I've never seen you happier, Baby-Joel.
Not all of Baby-Joel's memories are sad ones. He is really into sink baths, for example. If only we were all that small still… such a feeling of security. But we digress.
Quote #5
MARY: So you didn't do the erasing?
STAN: Of course not. God no.
MARY: And you never even suspected we were together?
STAN: Once, maybe. I was coming back from a job, and you were at his car. I saw you two talking. So I waved to you, and you giggled, you know.
MARY: How'd I look?
STAN: You looked happy. Happy with a secret.
Mary doesn't want to remember her affair with Howard only in order to avoid making the same mistake twice; she actually wants to keep the memories for the same reason Joel wants to keep his, specifically to remember her happiness (even if that happiness is ethically questionable).
Quote #6
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 f***ed-up girl who's looking for my own peace of mind. Don't assign me yours.
Clem is totally right. She knows that Joel thinks she will be able to make him happy by freeing him from his dull life. But even telling him straight up that they are in the same boat, both searching their own peace of mind, doesn't make Joel realize the truth.