TENTH DOCTOR: What? What?

SIXTH DOCTOR: What are you afraid will happen if you pause for breath?

TENTH DOCTOR: That there won't be another.

DOCTOR: I don't age. I regenerate. But humans decay; you wither and you die. Imagine watching that happen to someone that you-- [breaks off]

ROSE: What, Doctor?

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 Time Lords.

DONNA: Was it me, or was Isaac Newton hot?

DOCTOR: He was, wasn't he? He was so hot. Oh! Is that who I am now?

DONNA: Well, it was never that far from the surface, mate. I always thought…

“It's funny, cos I wonder where the TARDIS goes at random. Maybe it lands on some outcrop by the sea. And there's a tribe and they worship it for 100 years. Then they grow up and try to burn it. Then they get wise. They preserve it. Then they build a city all around it, till the TARDIS is just a tiny little dot, surrounded by skyscrapers and monorails. Time passes and the city falls. It all gets swept away. And there's the TARDIS… still on its outcrop… by the sea. She's the only thing I've got left.”

“It destroyed half the universe because of me. We stand here now on the edge of creation, a creation which I devastated. So, yes, I keep running. Of course I do. How am I supposed to look back on that?”

DOCTOR: A meteor storm. The sky above us was dancing with lights. Purple, green and brilliant yellow! Yes!

GRACE: What?

DOCTOR: These shoes! They fit perfectly. Yes.