A pessimist experiences the world as an unpleasant place. He expects the world to fall down on him, and if it doesn't, he does everything possible to help bring it down. He is unhappy with the way things are, and no matter what you try to do for him, it does not appear to make a difference in his outlook.

A pessimist is often the same outside of work as well. His favorite saying is "The tunnel will never end." Here's an example.

Neighbor: Congratulations! I hear your daughter is getting married.

Pessimist: It's another big expense for me.

Neighbor: But it's such a happy occasion.

Pessmist: Yeah, for everyone except me. I have to pay the bill.

Neighbor: Have a small wedding then. Your daughter is great. She'll understand.

Pessimist: Then everyone will call me cheap. You can never win. Things are always working against me.

The Solution

You probably won't be able to change a pessimist's attitude easily, so, for a start, focus on having him adopt some new specific positive habits to take the place of his existing negative ones. With practice and reinforcement, these new behaviors will gradually begin to replace the old ones.