I think the profile question "Do You Think the glass is half full or half empty?" needs a 4th choice. The glass is always full. But that choice is not given here, so I answered "Um..."
My professor in my psyche class in his introduction to his course brought up the half full half empty thing and said he would rather think "Hey, I've got a cup!" and see it as a positive regardless of what you are given.
When I am going through a bad spell like I was the last couple years it always made me smile and brought me back around to being positive and not giving up.