The real question is: Why is the glass is not completely full? Don’t you think?
Did someone not fill it right? Or did someone already drink half of it? Maybe the answer to whether the glass is half full or half empty lies in its past?
The glass really doesn’t matter. What you do with an empty or full glass tomorrow matters.
A pessimist doesn’t see possibility and so possibility passes him by often enough to confirm his belief. But well, at least he is prepared to suffer because it is only getting worse.
The optimist makes room for possibility and so possibility finds him often enough to confirm his belief. In the case of a bad outcome, he is positive he’ll manage it just fine. And so he does.
Fifty percent full is good enough to grant a 100% good result.