KALKIN: You're not old enough to have a granddaughter

DOCTOR: You're not old enough to be tired of life.

DOCTOR: I stopped running away from the bad things a long time ago, my life here meant everything to me.

LUCIE: You can't stay, you'll die if you stay!

DOCTOR: Everyone dies someday Lucie.

DOCTOR: Sometimes people don't want to be saved, sometimes, it's time to die, you should respect that.

DOCTOR: Out there in that city beneath us, that is the essence of life. It isn't just about the beat of our hearts, the breaths we take: it's our thoughts, our memories, our experiences - a myriad of emotions, family, friends, who we love, who we hate. The devolver takes all that away. To stop feeling and experiencing all these things is death, and if everyone around you has been destroyed then even the memory of your ever having lived ceases to exist - all that's left behind is nothing. Is that what you want?