I'm clearly insane
No reason to be sad. Practice your negotiation skills; use withdrawing as an opportunity to jerk the schools around for more money that wouldn't even change your mind. See if you can get a full ride, a stipend, etc. Make it a game.
Yeah. Part of it, for me, is the finality of closing off options. In some cases, where schools clearly went out of their way to do right by me, I feel genuine disappointment in dinging them.Of course, there are a few schools that ticked me off for being unhelpful, rude or extremely tardy, in which case my internal response to "We're disappointed" is "Good. Screw you." Ah, empowerment.