Elders call sleep is a temporary death and everyday morning after you wake up you should thank god for being alive for one more day. In ancient Greek mythology, Sleep was the twin brother of Death. It seems there was always an association between sleep and death. When people die in their sleep, it looks like an ideal way to pass off, without experiencing any pain of dying.
One-third of our lives are spent in sleep, so it does not come as a surprise when somebody dies in sleep. But there is a difference in a healthy person passing away in sleep and an ailing person expiring in sleep. If it is a natural death in peace then, it is considered a great boon.
Gone are the days when people die naturally due to old age. Due to the increased medical facilities, many people are living in ICU's on the medical support before they breathe last. It is a pain for the people around them and as well to the person who is suffering. In some cases, the medical expenses will be so high that the family of the dead person has to suffer lifelong under the debt trap.
It is fixed that everybody has to leave the world one day. If that happens peacefully in sleep, that is the best thing that can happen to a person.