A Paradigmatic Pessimist

Psychologists - I have been told - occasionally put a glass half full of water on the desk and ask the patient to describe what they see. The pessimists are said to be those who see not the visible plenitude but the lack, calling the glass half empty.

I confess: Show me a glass that is full to the brim and overflowing and I will say: "Hah! The glass is full now, but it won't be long before it is half empty."