You know that line of thought which says that you are able to tell whether someone is an optimist or a pessimist according to whether they think the glass is half-full or half-empty?
Well, nothing sh*ts me more than twee, trite nonsense such as this.
It really isn't such a deep question when you think about it.
A glass will always be half-full if you are filling it at the time. Ie, you are aiming to get the glass full, so half-way there is half-full.
Likewise, if you are aiming to empty a glass, half-way there is half-empty.
The appropriate description is dependent on the objective.
I mean, sure, you could be all 'normal' and relaxed about this and just take a commonplace saying for its intended meaning...
But I prefer the unnecessarily cynical and picky approach every time, thanks.
That is all.