I lost my own dad on this very day back in 2003. It's hard to believe it's been four years already.
Losing a parent (or both your parents in the space of a month - Jesus!) is disturbing on so many levels I wouldn't know where to start describing it. But it's really disconcerting on a particularly primal, selfish level that believes your parents are what stand between you and mortality. When they're gone, so is the barrier they created, and suddenly you're left staring at your own mortality with nothing in the way, no obstacles between you and it.
Anytime anyone dies, we're reminded of our mortality, but it's different when parents die. It's less a reminder than a save the date card.
Anyway, tonight I'm going out with some friends to celebrate my upcoming birthday. I'll drink a toast to my dad's memory, thank my lucky stars I still have a mom, and get nice and ripped. That'll show Death!