Drinking myself half way to full

A grab a glass and my favourite drink.
I pour it to the brim.
Slowly, I begin to sip my beverage.
I get about half way when I decide I’ve had enough.
I leave the glass where it is.
I don’t need anymore.
A person notices me just staring at the glass.
They ask why I don’t bother finishing this half empty glass.
Another comes over and tells me it’s still half full.
I look at both of them as say,
why can’t it be both?
Forget it, I’ll just finish it off.
At least then we know what it is.