Go down and eat some breakfast. Eat some lunch. Work until you drop. Microsoft explicitly focuses on morale. Each group at Microsoft has a morale budget that can be used for anything the group wants to use it for.
Some groups buy movie-theater style popcorn poppers.
Some groups go skiing or go bowling or have a cookout. Some groups make T-shirts. Some groups rent a whole movie theater for a private screening of their favorite movie. When I first began consulting at Microsoft, I was pleasantly surprised to find how much time each day I could actually spend working. You just take what you need, and you don't even need to sign anything.