Anniversaries.

Ever since I could remember, we've been celebrating certain events or people. I want to know what brought this tradition upon our society. Seriously, since when must we commemorate such an event? Is remembering not adequate enough for such an affair?
Lets say something terrible happens. For the sake of arguement, your mother just passed. Of course your thoughts are of nothing but her- most presently, her death. Why must you devote an entire day each year for her death? I mean, if it had been me, I would honor her daily instead of on special dates only. You picking up what I'm putting down?
Apparently I was going nowhere with this- my friend says so ;)- just a sort of rant. Maybe I need sleep =D