I couldn't possibly choose just one book. Nor just one quote!
So here are some of my favourites, in no particular order:
"It's an odd thing, happiness. Some people take happiness from gold. Or Black pearls. And some of us, far more fortunate, take their happiness from periwinkles."
"I don't want whatever I want. Nobody does. Not really. What kind of fun would it be if I just got everything I ever wanted just like that, and it didn't mean anything? What then?"
"But it's hard to leave a place when you're tied to it by fear, when it's broken you with fear, when it's all you've ever known."