"There are, it has been said, two types of people in this 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)