Not really sure. It wouldn't hit me immediately, since big things don't always register with me for some reason. That'd be a few days to a week of normal activity. Afterwards, I'd probably be very moody, going from bouts of bitterness and lashing out, self-pity, apologizing to others for my behavior, get an upbeat attitude with certain interactions with people, but then I'd realize that I'm not gonna SEE those people for very long, and I'd get pissy again. During maybe the last two weeks, I'd go back and forth between feelings of immortality, thinking there's NO way I'm really going to die, to begging and pleading with God for mercy, forgiveness at anything I've done wrong, or a way out. I'd probably do that until the end, along with get stressed out about trying to talk with as many close friends/family members/loved ones as possible for "the last time". Goodbyes are something I've never been good at. Then, as the end draws near, I'd make it a point to make sure I died in a "dignified" position, something that would be photoworthy, like sitting at a desk, maybe with a pen in my hand, or a burned-out cigarette. This would also stress me out, because I'd have to guesstimate when I would be dying, and I'd waste a lot of my last hours sitting around with a dumb look on my face, waiting. In the end, I think I'd die when I least expected it, probably on the kitchen floor or in the shower, or something stupid like that.
I don't think I'm quite emotionally mature to accept death, yet. 😉