Happiness declines during puberty and middle age, peaking around age 50. After that, it goes back to the mid-60s again. Then something strange happens. Older people split into two groups as they get older: they are becoming happier, and they are becoming more unhappy.

Around this time in life, many people realize the importance of making sound financial decisions in their earlier decades. Those who planned ahead and survived are more likely to be able to support themselves comfortably; Many of those who didn’t, can’t. Something similar happens with happiness, as I show in my new book From Strength to Strength: Finding Success, Happiness, and Deep Purpose in the Second Half of Life.

Each of us has something like a “happiness 401(k)” that we invest in when we’re young, and that we enjoy when we get older. And just as financial planners advise their clients to engage in specific behaviors—automate your savings; Think twice before you buy that boat—we can all teach ourselves to do some very specific things at any age to make our last decades happier.

In 1938, Harvard Medical School researchers shed light on a visionary idea: They would sign up a group of men and then study at Harvard and follow them from puberty to adulthood. Every year or two, the researchers asked the participants about their lifestyle, habits, relationships, work, and happiness. The study has since expanded to include people beyond men who went to Harvard, and its results have been updated regularly for more than 80 years. Those results are a treasure trove (and I’ve referenced them several times in this column): You look at how people lived, loved, and worked in their 20s and 30s, and then you can see That’s how his life turned out over the following decade. And from this crystal ball of happiness, you can learn how to invest in your future well being.

As participants in the Harvard Study of Adult Development got older, researchers classified them in relation to happiness and health. Populations vary greatly, but two distinct groups emerge at the peak. The best are the “happy-well”, who enjoy good mental health and high life satisfaction, along with good physical health. At the other end of the spectrum are the “sad-ill,” who are below average in physical health, mental health, and life satisfaction.

When they were younger, happy seniors pooled some of the resources and habits in their happiness 401(k)s. Some of this, like generational wealth, is difficult for each of us to control: having a happy childhood, descending from long-lived ancestors, and surviving clinical depression.

But some are, to varying degrees, within our control, and they can teach us a lot about how to plan for late-life happiness. Using data from a Harvard study, two researchers in 2001 showed that we can directly control seven big investment decisions: smoking, drinking, body weight, exercise, emotional resilience, education, and relationships. Here’s what you can do about each of them today to make sure your accounts are as complete as possible when you reach your later years:

Don’t smoke – or if you already smoke, quit now. You may not be successful on your first attempt, but the sooner you start the process of quitting, the more smoke-free years you can invest in your happiness account.

Watch your drinking. Alcohol consumption is strongly correlated with smoking in a Harvard study, but a lot of other research shows that even in itself, it is one of the most powerful predictors of end-sickness. If there’s any sign of a drinking problem in your life, get help now. If drinking is a problem in your family, don’t take the risk: Keep that switch off. Although quitting alcohol can be difficult, you will never regret making that decision.

Maintain a healthy body weight. Eat a diet with plenty of fruits and vegetables and moderate intake, but avoid yo-yo diets or intense restrictions that you can’t sustain for long.

Prioritize the pace in your life by making time for it every day and sticking to it. Arguably the single best, time-tested way to do this is by taking a daily walk.

Practice your coping mechanism now. The sooner you can find healthy ways to deal with life’s inevitable crises, the more prepared you will be if bad luck strikes in your 80s. This means working consciously—perhaps with the help of spiritual practices or therapy—to avoid excessive rumination, unhealthy emotional reactions, or avoidant behavior.

Keep learning. More education leads to a more active mind in old age, and that means a longer, happier life. That doesn’t mean you need to go to Harvard; You just need to engage in lifelong, purposeful learning. For example, this might mean reading serious non-fiction regularly to learn more about new topics.

Work now to develop stable, long-term relationships. For most people, this includes a stable marriage, but other relationships with family, friends, and partners can also fit into this category. The point is to find people you can grow with who you can trust, no matter what comes your way.