To quote Pratchett:

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!

To put it simply:

There are three kinds of people in this world.

The optimistic.

The pessimistic.

And the assholes.

And if he's right, the world belongs to these selfish people.

I would like to believe in it too.

But not so soon.

I've got a clear conscience, while you, dearest, can find your own tissue when you're in deep shit.