sick of that glass

Wherever I post, somebody always ends up telling me that there are 2 kinds of people, the kind that sees the glass half full and the kind that sees the glass half empty. I have just realized that the truism is wrong. there is another kind. there are some, that everytime they get some water in the glass, someone jogs their elbows and the water spills. they are just trying to keep water in the glass. does that metaphor help to understand that optimism/pessimism are not an issue for spectrum?