see i take it as a half full or half empty thing, its all a matter of perspective, if you think you are nothing then go on thinking you are nothing, but if you think you mean something then you do. People who think their worthless are because all they do is bring people down with them , like the phrase misery likes company, by the way the whole half empty half full thing, i came up with a logical answer.

if your pouring/drinking/lessening the ammount in the glass, then its half empty, if you are adding stuff to it then it is half full, and if somehow half of the space in the glass was occupied then clearly the glass is twice as big as it needs to be.