In hundreds of well-controlled studies, positive emotions have been shown to contribute to success at work, improve immune function, and lead to a longer life and overall well-being.

The “nun study” is a perfect example. Twenty-year-old nuns began keeping journals of their thoughts and feelings. Five decades later, these journals were analyzed for positive and negative emotions. The women with more positive emotions lived more than 10 years longer than those with more negative emotions. At age 85, 90 percent of the happiest nuns were alive, while only 34 percent of the least happy lived.

People who experience positive emotions have less pain and disability related to chronic health conditions, fight off illnesses more successfully, have lower blood pressure, and less stress associated with negative emotions. Positive emotions are also linked to resilience. People who experienced positive emotions before the 9/11 attacks recovered faster from trauma than their less positive counterparts. Optimism buffers against the negative effects of traumatic events, because it fosters active problem-solving and constructive action.

Positive emotions activate biochemical changes in the brain. Positive emotions flood our brains with dopamine, serotonin, and endorphins, neurotransmitters that stimulate the brain’s reward system and are associated with positive moods, motivation, pleasurable sensations, and enhanced cognitive abilities.

The “broaden and build” theory offers an explanation of the salutary effects of positive emotions. Fear and stress activate the “fight, flight, freeze” response for survival purposes, restricting our thoughts and actions. When we have negative emotions we have a narrowed range of thought–action responses; we are in quick and immediate stress mode. Conversely, positive emotions lead to broadened and more flexible responses, widening the array of thoughts and actions that are possible. We are more thoughtful, creative, and open to various intellectual, social, and physical resources.

Creating a positive mindset before a task or experience has been shown to produce positive results. Adults who are “primed” for positive emotions before an experiment have more creative and diverse ideas and solutions than those not primed. High school students who were told to think about the happiest day of their lives before taking a math test did much better than students not positively primed. Four year olds were asked to complete several learning tasks, such as assembling different shaped blocks. The children who were told to think about happy situations prior to the tasks did much better than those not primed.