Each moment is lost time, lost opportunities or possibilities or potentialities. If one chooses to view it that way, each passing second is the removal of branching potential tracks that life could take, a narrowing of options, or perhaps a fatalistic focusing that approaches something like binding destiny.
But to see things as such is maddening.
So instead we grieve the near-concrete. When I was a child, I understood my great-grandmother's death as not the loss of her, per se (for I have memories! and photos! and heaven to look to!) but rather I understood it as the loss of being able to hug her, to feel her love for as long as I would choose to hold on. That was the threat of death.
While I was at home, I grieved and shared in my family's grief. It hurts to lose and there is a lot of loss we could hurt over. But mainly my family shared the time that is rushing past us, and we love as we choose to hold on.
Grief was just one part of the trip home, and grief is always a part of life going on.