There is nothing either good or bad, but thinking makes it so.

Actually the full quote is a little different, but I had to make it a tad shorter and modernized. The full quote is:

Well, then it isn’t one to you, since nothing is really good or bad in itself—it’s all what a person thinks about it. And to me, Denmark is a prison.

Part of Act 2, Scene 2, Page 11 of Hamlet where  Claudius and Gertrude host Rosencrantz and Guildenstern, whom are Hamlet’s friends coming from Wittenberg. Concentrates on Hamlets erratic borderline crazy behavior.