I know it's extremely geeky, but in my journal I use the number of days since I was born as a kind of "stardate". For example today (for me) is day 10872. I'm 29, it's been a little over ten thousand days since I was born, and I figure I've got at least another ten thousand or so barring some unforeseen accident or illness.

Seemed kind of pointless to do this at first, but this "numbering convention" stuck with me because it lets me keep in my mind the idea that I _do_ have a limited number of days left on this earth -- and I'd better make the most of them!