Point of view
I don't tend to see the glass as half-full or half-empty. I see it as containing a liquid which appears to be water and therefore (if true) possibly useful if one were thirsty or wanting to cook or do other chemical work, but also presenting a hazard by aspiration or slippage (if spilled), and dangerously fragile, and too close to someone's elbow.
no subject
Pessimist: Glass half empty
Realist: Glass twice the size it needs to be
Opportunist: Drinks the water while the optimist, the pessimist and the realist are busy arguing about it.