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! Who's been pinching my beer?	And at the other end of the bar the world is full of the other type of person, who has a broken glass, or a glass that has been carelessly knocked over (usually by one of the people calling for a larger glass) or who had no glass at all, because he was at the back of the crowd and had failed to catch the barman's eye. 
Terry Pratchett, The Truth
life