Positive, optimistic sales people sell more than pessimistic sales people.

People who believe they cause good things tend to like themselves better than people who believe good things come from other people or circumstances.

There are physical characteristics which are inherited. These include things like good looks, high intelligence, physical coordination. These attributes contribute to success in life, and success in life is a determinant of optimism.

Changing the destructive things you say to yourself when you experience the setbacks that life deals all of us is the central skill of optimism.

By activating an expansive, tolerant, and creative mindset, positive feelings maximize the social, intellectual, and physical benefits that will accrue.

Some find that very optimistic people have benign illusions about themselves. These people may think they have more control, or more skill, than they actually do. Others have found that optimistic people have a good handle on reality. The jury is still out.

On the relationship side, if you teach people to respond actively and constructively when someone they care about has a victory, it increases love and friendship and decreases the probability of depression.