Lennon

“When you run with the Doctor, it feels like it'll never end. But however hard you try you can't run forever. Everybody knows that everybody dies and nobody knows it like the Doctor. But I do think that all the skies of all the worlds might just turn dark if he ever for one moment, accepts it. Everybody knows that everybody dies. But not every day. Not today. Some days are special. Some days are so, so blessed. Some days, nobody dies at all. (In the library, the Doctor walks back to the TARDIS. He stops, looking at the doors. Then he raises his hand, and stands there poised like that for a long moment. Finally he snaps his fingers. The doors open. He smiles slowly and walks in, joining Donna. Then he snaps his fingers again, and the doors close. River's voice continues over this.) Now and then, every once in a very long while, every day in a million days, when the wind stands fair, and the Doctor comes to call... everybody lives.”
― Steven Moffat

“Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you.”
― Friedrich Nietzsche

“A man can be himself only so long as he is alone; and if he does not love solitude, he will not love freedom; for it is only when he is alone that he is really free.”
― Arthur Schopenhauer, Essays and Aphorisms

“Hell is—other people!”
― Jean-Paul Sartre, No Exit