"...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..."

..."Is that any reason to bring him to Court? Hey?" Trumpkin to the Owl (Glimfeather), who was introducing Eustace, in The Silver Chair.

"We've done the silliest thing in all the world by coming at all..."