"The best life is spent preparing for death." Plato
Not very optimistic or comforting, so why say it?
Pretty simple, all life eventually dies, there's no avoiding it. If you have a problem with death then you have a problem with life. Noone living, leaves life alive... and we've all got to leave!Maybe death is the meaning of life, not salvation, or worshipping Allah or even biological reproduction, as these experiences aren't even that universal within life! In a world where death is so universal it's only sensible to contemplate and prepare for death.

Now this doesn't mean we should commit suicide. I'm not, life's too interesting! No, death comes whatever, suicide or not so there's no need to commit suicide. Personally I'd much rather die after a long and complex life that cut it short.

I've heard it said that we start dieing the day we are born. It's like we've been given a death sentense from birth. The only difference between "most people" and those who ARE on death sentence or who are terminally ill is that "most people" are less aware of their mortality.

Death is the ever present, silent companion that makes life real. Imagine immortality, without death. It would be dull and boring. It is mortality that makes life intense and vibrant instead of the same dull grey forever. Paradoxically those who are acutely aware of death can find a new zest for life not found when blind about mortality.

Another quote comes to mind though I don't remember who said it "Live each day like it's your last."