In a conversation with Rosencrantz and Guildenstern, who visit him under the guise of solicitude, Hamlet banters words. One of the replies that he gives to their insincere responses is
Why then 'tis none to you; for there is nothing either good or bad; but thinking makes it so. (II,ii,241-242)
So, you may wish to examine the power of thought in "Hamlet" since Hamlet often engages in self-debate [Consider his famous "to be" soliloquy, and later he asks himself "Am I a coward," (II,ii,528) etc.] That is, how much does Hamlet's introspection and self-debate affect his actions/delay of actions and his tragic demise?