Death

I believe there are 3 ways a person dies.
1. Murder
2. When they figure out what life's about.
3. When they mentally can't handle it anymore.

1. Murder: Karma generally. You do something stupid, you die. Simple enough. Or when you're times about up and someone else needs to be punished.
2. When a person figures out what life's about, there's no reason for them to continue living, so they die. Accidents, heart attacks, heat strokes, etc...
3. Your mind can only handle so much, and when your mind hits the limit, times up. Which is a lot of the reason we don't remember our past lives. Unless we died prematurely by being murdered. Then we can remember some of our pasts. Suicide fits under this category as well. People kill themselves when they mentally can't handle it.