Mood evidently affects the operation of System 1: when we are uncomfortable and unhappy, we lose touch with our intuition. These findings add to the growing evidence that good mood, intuition, creativity, gullibility, and increased reliance on System 1 form a cluster. At the other pole, sadness, vigilance, suspicion, an analytic approach, and increased effort also go together. A happy mood loosens the control of System 2 over performance: when in a good mood, people become more intuitive and more creative but also less vigilant and more prone to logical errors.

Experts don't know exactly where the boundaries of their expertise are.

However, optimism is highly valued, socially and in the market; people and firms reward the providers of dangerously misleading information more than they reward truth tellers. One of the lessons of the financial crisis that led to the Great Recession is that there are periods in which competition, among experts and among organizations, creates powerful forces that favor a collective blindness to risk and uncertainty.

Every night for the next week, set aside ten minutes before you go to sleep. Write down three things that went well today and why they went well...Writing about why the positive events in your life happened may seem awkward at first, but please stick with it for one week. It will get easier. The odds are that you will be less depressed, happier, and addicted to this exercise six months from now.

If you can't take the time for a vacation right now, or even a night out with friends, put something on the calendar - even if it's a month or a year down the road. Then whenever you need a boost of happiness, remind yourself about it.

Facts that challenge basic assumptions-and thereby threaten people's livelihood and self-esteem-are simply not absorbed. The mind does not digest them.

True intuitive expertise is learned from prolonged experience with good feedback on mistakes.