Death is simply a shedding of the physical body like the butterfly shedding its cocoon. It is a transition to a higher state of consciousness where you continue to perceive, to understand, to laugh, and to be able to grow.
Mourning can go on for years and years. It doesn't end after a year, that's a false fantasy. It usually ends when people realize that they can live again, that they can concentrate their energies on their lives as a whole, and not on their hurt, and guilt and pain.