One of the big changes in psychology over the course of my career has been the increase in research on positive psychology. When I was a graduate student, there was a lot of work on stress and mental illness, but few researchers spent much time studying happy people.
Quite a bit of research has examined influences of positive affect on thinking. Positive affect is the broad term used to describe the variety of positive feelings that people experience. For example, work by Alice Isen and her colleagues found that positive affect made people more creative and more likely to be helpful relative to a neutral mood.
What happens over a long period of time, though? It is possible that the benefits of being happy persist over the long term and happy people are the ones who make the most of their lives. It is also possible that there are benefits to being happy in the short term, but not in the long term. Perhaps people who are uncomfortable with their life as it is now are more likely to pursue educational and career opportunities to improve themselves than people who are happy.
So what happens?
This issue was explored in a study in the August, 2012 issue of Personality and Social Psychology Bulletin by Claudia Haase, Michael Poulin, and Jutta Heckhausen. In one study, they analyzed data from a long-term series of questionnaires given to high school students as they prepared to graduate and in the period just after graduation. At each of six time periods, students rated how much positive and negative affect they were experiencing. They also rated how much they were devoted to working hard for their future occupation. Students also rated how many internships or apprenticeships they applied for and how many they received.
For each time point in the survey, the researchers used statistical analyses to predict the degree of effort people were putting in toward their career. Obviously, the best predictor of the amount of effort you are putting toward developing a career is how much effort you have expended in the past. Once you control for past effort, though, the next best predictor is the amount of positive affect you experienced in the past. The amount of negative affect you experienced did not predict effort significantly. A similar pattern was obtained for analyses of the number of apprenticeships applied for and obtained.
Overall, when people are happy, they put in more effort to create a better future for themselves than when they are not happy.
Why does that happen? Putting in effort for the future is a risk. That effort may not be rewarded. In order to feel confident that the effort will be repaid, you have to believe that your effort will overcome the obstacles to success. Positive affect helps people to believe that obstacles are surmountable and that effort put in for the future will lead to success. Without that positive affect, people are less confident that it is worth it to work hard for their future.