I've read The Great Gatsby I don't know how many times. You'll have to do better than that.
"To kill me, you would have to become solid. And when you become solid, you can be broken."
This is going to be a tough one unless you're familiar with the source.
EDIT: I didn't have that exactly right. The lines reads: "To kill me, you would first have to become solid. And when you become solid, then you can be broken." Still, close enough IMO.