Like all of us, I'm living under a death sentence. Not to sound alarmist, but to quote Woody Allen in "Love and Death": "Isn't all mankind ultimately executed for a crime it never committed? The difference is that all men go eventually, but I go six o'clock tomorrow morning." Looking on the bright side of death, I think in some ways it must be nice to have such certainty. But we live in perpetual uncertainty and doubt (see "No Country for Old Men"). My own awareness of the prospect of my demise ranges between roughly five years and five seconds, according to fluctuations in the health of my heart. I've gotten close enough to peer over the threshold (and in one case, lost my grip and fell into the void for, I'm told, about 10 or 15 minutes). My point is, I don't see death as an abstraction but a... vividly imminent possibility, depending on the situation.
(Neuroscientists say it may take the human brain 20-30 years or of development to really begin to fathom the concept anyway -- to some extent we tend to feel, and behave, as if we are immortal before that. I think my brain "knew" somewhat earlier.)
My adventures in mortality are absolutely nothing, however, compared to what some of my friends and acquaintances have been through. People have asked me if my near-death (temporary-death?) experience in 2000 gave me a new perspective on life and I have to say... no. I've been preoccupied with death ever since I was old enough to have a rudimentary understanding of what that was. It used to make me a little dizzy thinking about an infinity of nonexistence, like the one I didn't experience before I was born, but I don't find anything disturbing or frightening about that. Hey, it happens to everybody. Dying is easy; living is hard.*