Since 2008, The Harris Poll has surveyed Americans to assess their level of general happiness. Their Happiness Index is an average from responses that agree strongly with positive statements (about good relationships with family and friends, health and general happiness) and disagree strongly with negative statements (about anxiety, money, politics, work and pastimes). During the eight years since the index’s inception, the joy in America has stayed in the mid-30s (out of 100), which means that only one in three Americans see themselves as happy. This year’s results for are even worse: Happiness in the U.S. has dropped to 31—an all-time low.

That’s an “F” for happiness by standard American school grading. How could Americans become happier? Neuroscientists estimate that the human brain is made up of between 86 to 100 billion neurons. As we age, the brain produces new neurons, creating new neural connections, a process called “neuroplasticity.” This plasticity is advantageous because it means the brain is malleable, capable of being shaped and altered.

This means that we can be happier if we shape new neurons in a certain way. Granted, a large part of our happiness depends on our luck in the genetic draw because we’re born with a happiness level pre-determined by our genes. But that doesn’t mean we have to stay stuck at that predisposed level. Center for Healthy Minds founder Richard J. Davidson, a pioneer in affective neuroscience, says “We know that the brain’s structure and function can change throughout life, even as adults. It means you can train your brain to better manage which emotions surface when and for how long.”

This premise is the basis for Joy on Demand, the new book written by SIYLI’s founder Chade-Meng Tan and the foundation of our new Joy on Demand programs, which premiere this fall in San Francisco, Toronto, New York City, Los Angeles and the Silicon Valley. The program teaches how to tap into a sustainable source of happiness—from within ourselves—and how to retrain our brains to do it. Even if you’re in the fortunate 31 percent of Americans who are already happy, there’s no such thing as too much happiness.

Extra reading for those outside the United States: World Happiness Report 2016. Spoiler alert: The Danes are the happiest.