Doctor: You lost someone.
Rogue: How do you know?
Doctor: Because I know.
Rogue: We travelled together. We had fun. Then one day, when it came to the end of the day...
Doctor: I lost everyone.
Rogue: I saw you at the party, dancing with that woman.
Doctor: My best friend.
Rogue: Do you ever wonder... why keep going?
Doctor: Because we have to. At the end of the day, we have to keep going because they can't.