If we really look, we can find some rather interesting answers.
I’m talking here about an actual glass, but the same could be applied to the commonly used metaphor.
The first thing that’s obvious is that the half-emptiness and half-fullness are always both present.
When a glass is half full, it is, simultaneously, half empty.
To label it either way is only to acknowledge on side to the exclusion of the other, but in reality, half empty implies half full and vice versa.
Now, let’s take it a step further.
Is it really either of those?
The glass itself does not know empty or full, nor does it know anything of the water it contains.
Likewise, the water itself knows nothing of the glass.
Emptiness and fullness have nothing to do with the objects in and of themselves; rather, they are labels that we assign.
Does our labelling make it so?
Does your projection onto something make it as you believe it to be, beyond the belief?
Does it have absolute truth to it, or can it ever be relative?
And if so, relative to what?
This is all equally present in the way we view each of the situations, circumstances, experiences, people and everything else in our lives.
So, ask yourself again, is the glass half empty or half full?