"Importance Of Someone's Absence"

Why do we miss a person?

It's either:

We realize that we never treasured the moments when they were always there, and it left us wishing we could turn back time again.

Or...

We were too happy with them, we enjoyed every single moment taht we became so used to the idea of having them around. But when we finally walked separate lives, we realized that a moment spent with them is like dying stars which slowly leave the sky...empty.