"...what they truly seek." - Emeth (quoting Aslan's words to him), The Last Battle.

"Even if I can't stop blubbing, I won't..."

"...I won't get my string wet..." - Jill Pole, The Last Battle

"Men like me who possess hidden wisdom, are freed from common rules just as we are cut off from common pleasures. Ours, my boy, is..."

~ Wunder

"...a high and lonely destiny." - Uncle Andrew, The Magician's Nephew.

"No more of that, Your Majesty..."

"... if you love me." - Trumpkin (to Edmund), Prince Caspian

(Finally, after puzzling over this one on and off for 18 months or so...!! I just looked at this thread again this evening and suddenly realised it sounded like Trumpkin, so I went looking, and there it was. I'll try to post a reasonably easy one — I hope — to keep the game going...)

"But you'd better be lying dead tonight..."

“than go to be a human slave in his house tomorrow”- Bree, The Horse And His Boy.

”All worlds draw to their end…”

"... except Aslan's own country." (Jewel in The Last Battle)

"A King who has just won a great battle can usually establish himself..."

"... without the help of a performing lion." (Nikabrik in Prince Caspian)

"I'm going to live as like a Narnian as I can..."

.."even if there is no Narnia". (Puddleglum, in The Silver Chair)

"Many fall down...."

"... and few return to the sunlit lands." — The Warden of the Marches of Underland, in The Silver Chair

She would have smashed that whole world, or all worlds, to pieces...

..."if it would only stop the singing." - Jadis the White Witch, in the Magician's Nephew.

"I will not be talked to like that, by a little, dirty, schoolboy"...

"... You don't understand. I am the great scholar, the magician, the adept, who is doing the experiment...." — Uncle Andrew in The Magician's Nephew.

(His speech goes on for a fair way after that, so I hope I've put in enough for it to count! )

"And we beasts remember, even if Dwarfs forget..."

"...that Narnia was never right except when a son of Adam was King." ~ Trufflehunter in Prince Caspian.

"By the Lion's Mane, a strange device..."

... said King Peter, "to set a lantern here where the trees cluster so thick about it and so high above it that if it were lit it should give light to no man!" — The Lion, the Witch and the Wardrobe

"Well, there are the clothes, for one thing. And..."

"... you have been—well, undragoned, for another." ~ Edmund to Eustace, The Voyage of the Dawn Treader

"Useless?" said the Dwarf irritably. "I dare say he is. Is that any reason..."