Stay in bed all day. Literally. Spend an entire 24-hour period lazing around in bed. Have breakfast in bed, read magazines, take naps, or paint your nails. I can guarantee you will never have another day like that again, unless you’re actually sick, and where's the fun in that?
Be selfish. You're hot and everyone else is cold? Sucks to be them. Don’t have any qualms about cranking up that A/C.
Say yes to a spontaneous plan. When your friend offers you an extra concert ticket two hours before the show starts, accept it on the spot. Once you have a kid, you won't have the energy to make the 23 calls necessary to free up your schedule.