Is your glass 1/2 empty or 1/2 full?

Actually, if the glass represents time, then it is less than half full, much less.
The other question is what's exactly in the glass, metaphorically?
 
It's all about direction.

If it was last poured into - it's half full.

If it was last poured out of - it's half empty.
 

Mathematically, it's both.

This reminds me of an instance when I was in a diner, and at the table next to me, a waitress asked the fellow if he wanted more coffee.

"Just half a cup."
"You want it half empty or half full?"
"Half empty. I don't think I could drink it all if it was half full."

Pretty funny.
 

Back
Top