It begins at 40. A U-Mich Study says people consistently underestimate the sweetness of adulthood.

“People often believe that happiness is a matter of circumstance, that if something good happens, they will experience long-lasting happiness, or if something bad happens, they will experience long-term misery,” says Peter Ubel, M.D. “But instead, people’s happiness results more from their underlying emotional resources — resources that appear to grow with age. People get better at managing life’s ups and downs, and the result is that as they age, they become happier — even though their objective circumstances, such as their health, decline.”

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