half cup empty is pessimism,which means you're VERY negative.half FULL is the exact opposite.it is OPTIMISM,which means you're VERY positive about things.for example,"Today ____ is seeing the glass half full whereas his brother ____ is seeing the glass half empty.".
its a figure of speech that means you are a pessimist or basically always looking at the down side of things. cup is half full is the opposite and that you are an optimist and that you always look on the bright side of things.
It's all a matter of semantics... merely different ways of saying the same thing. But someone who views the glass as half full is seen as an optimist, while someone who views the glass as half empty is seen as a pessimist.
Its pretty much the same thing. When its half full I guess its when someone pours a cup halfway. And when its half empty its when theres a cup filled to the top and someone drinks half of it its half empty, thats what I think.