Doctor Who 'The end of Time'

The Doctor: "I am going to die."
Wilf: "Well so will I some day."
The Doctor: "Don't you dare."
Wilf: "Alright, I'll try not to."
The Doctor: "But I was told. He will knock four times. That was the prophecy. Knock four times and then-"
Wilf: "Yeah but I thought, when I saw you before, you were saying that your people could change like your whole body."
The Doctor: "I can still die. If I am killed before regeneration then I am dead. Even then. Even if I change it feels like dying. Everything I am dies. Some new man goes sonthering away. And I am dead."
[...]
Wilf: "How about you? Who do you've got now?"
The Doctor: "No one. Traveling alone. I thought it'd be better... But I did some things. It went wrong. I need-"
Wilf: "Oh my word, I'm s-"
The Doctor: "Merry Christmas."
Wilf: "Yeah, and you."