Why do we sit shivah for seven days? Because the world was made in seven days and each person is a world, a world that never was before and that will never be again. If death is not something to be marked for a week because it is so awesome an event, if death is nothing, if death is cheap, then life is cheap. So the tradition says: Stop whatever you are doing and take notice, mourn, work it out, talk it out, for seven days. No more and no less.
— Jack Riemer, Wrestling with the Angel by Jack Riemer, editor