Our condolences. It doesn't seem to matter how old they are, or how old we are, we're never ready to lose a parent.
When it hit me the hardest after my Dad passed, was that first Father's Day. I started thinking, "I should call Dad today," before realizing that wasn't an option any longer. It's been over twelve years, and I still wish I could call him.
I used to call him on my way home from the field to tell him what I flew, who I saw, how I did in combat, etc...Can't do that anymore. I'm still getting used to that, and I know it's going to be hard.