The ancient Egyptians may have built elaborate funerary complexes but they were neither obsessed with death nor afraid to die. Instead, the ancient Egyptians believed that life was part of the natural cycle, like the changing of the seasons, and that a person's akh or spirit lived on in the afterworld. The passage from Kingdom of the Living to the Kingdom of the Dead, however, was not guaranteed. The ancient Egyptians believed that resurrection was achieved only if the deceased's ba (persona) and ka (life force) were reunited each night. To ensure this, they took elaborate steps to preserve (mummification) and safeguard (tombs and pyramids) the dead. What's more, the ancient Egyptian's filled the deceased's tomb with lots of food and drink as well as all of things he made use of in life as they would be needed again in the next world.