Rose Tyler: I’ve been to the year five million, but this, this is really seeing the future- you just leave us behind! Is that what you’re going to do to me?
The Doctor: No. Not you.
Rose Tyler: But, Sarah Jane- you were that close to her once, and now… you never even mention her. Why not?
The Doctor: I don’t age. I regenerate. But humans decay. You wither and you die. Imagine watching that happen to someone you…
Rose Tyler: What, Doctor?
The Doctor: You can spend the rest of your life with me. But I can’t spend the rest of mine with you. I have to live on, alone. That’s the curse of the Timelords.