It's a tough question, and one that I think everyone struggles with.
I have several thoughts about it though:
1) It's natural to fear and want to do anything to avoid death. It's embedded in our biology, and the driving force behind the survival instincts of every creature on Earth.
2) Everyone is certain to die at some point. That's why it's important to make the most of your time.
3) If you are religious, then most religions believe there is an afterlife, or that death is not the end.
4) In the grand scheme of things, we are so utterly insignificant that the life of even the most important person on the planet is still only a tiny minuscule speck in the timeline of existence.
I don't know why, but I find this last point strangely comforting. No matter how crazy the world gets, or how many people come and go, everything you will ever experience in your lifetime is only a tiny inconspicuous speck of dust in time and space.
