RIVER: It's hard to leave when you haven't said goodbye.

DOCTOR: Then tell me, because I don't know. How do I say it?

RIVER: There's only one way I'd accept. If you ever loved me, say it like you're going to come back.

DOCTOR: Well, then. See you around, Professor River Song.

RIVER: Till the next time, Doctor.

DOCTOR: Don't wait up.