Lots of people ask, “Is the glass half-empty or half-full?” as a measure of pessimism vs. optimism.
I say it matters on what the glass was like before you just showed it to me. If it was empty, and you put water in, it’s half-full. If it was full, and you dumped some out, it’s half-empty.

Wow, Chris that’s really profound. Did you just come up with that or did you read it somewhere?
Thanks for ruining that question for me for the rest of my life.
It’s something that I thought of a LONG time ago, but never wrote until now. I was just reading a different website looking for a recipe for beer can chicken and it said:
and I thought to myself, that wouldn’t be half full, that would be half empty, so I came here to write about it.
Good observation! I like how your extension of this overused adage fits into everyday life; if you’re really depressed and someone cheers you up, they’re effectively “filling your cup”. Likewise, if you were in a great mood and you get some bad news, your cup has been similarly emptied.