"There are, it has been said, two types of people in the world.  There are those who, when presented with a glass that is exactly half full, say: this glass is half full. And then there are  those who say: this glass is half empty.

The world belongs,  however, to those who can look at the glass and say: What's up  with this glass? Excuse me? Excuse me? This is my glass? I don't  think so. My glass was full! And it was a bigger glass!" -- Terry Pratchett, "The Truth"