Studies show that people who are happier tend to also be healthier and live longer [PDF]. But how do you become a happier person? 

Over at Scientific American, psychologist and science writer Scott Barry Kaufman summarizes the main characteristics of “optimal” humans—that is, people who are the healthiest and happiest—using a 2004 textbook called Optimal Human Being by University of Missouri psychologist Kennon Sheldon, who studies well-being and positive psychology [PDF

Kaufman distills Sheldon’s research overview into rules for being an optimal person, based on recent studies. Here are three things he suggests that people should do to be as happy as possible: 

1. SET GOALS FOR YOURSELF.

In order to feel like you’re moving forward with your life, you need to have goals to work toward. However, they can’t be just any goals. 

Goals that are pursued because they fit in with your overall values and interests, rather than because of some outside influence, are said to be self-concordant. For instance, you’re in medical school because you really want to join Doctors Without Borders, rather than because your parents want you to make a good living as a doctor or you feel it will help your social status. Or you spend all day at ice skating practice because you love the sport, not just because you’ve done it since you were a toddler and think you should.

In a 2004 study, Sheldon and his team found that self-concordant people reported higher subjective feelings of well-being across four different cultures, both in the Western world and in Asia. In other words, working toward goals that are based on genuine interest is an important part of happiness. And even if your goals don’t exactly align with your sense of self, they need to at least provide “regular experiences of autonomy, competence, relatedness, self-esteem, and security that all humans seem to need,” as Sheldon writes in his book.

2. TRUST YOUR INSTINCTS.

How do you know whether you’re pursuing goals that are good for you? According to Sheldon, the key is listening to your “organismic valuing process” (OVP), or that innate sense of what is important to you and what is necessary for you lead a more fulfilling life [PDF]. This is the nagging little voice in your head that says that something doesn’t feel quite right. “Consult one's [organismic valuing process] when making goal choices, to try to determine what is best,” Sheldon advises in Optimal Human Being. “After making the decision, embrace the goal as thoroughly as possible (i.e., intentionally align one's sense of self with the goal). However, remain open to the OVP, so that as new information comes in, one is able to recognize any emerging necessity to make changes.”

3. LOOK OUTSIDE YOURSELF.

While it’s important to seek personal fulfillment, helping others will make you feel good, too. Research has shown that being generous can make you healthier and happier. Volunteering and other acts of altruism are linked to maintenance of your psychological well-being. And linking your goals to something larger than yourself also impacts how connected you feel to the rest of society. “Pursue higher level (social, cultural) goals—that is, attempt to align your personal action system with the action systems of others or of cultural institutions,” Sheldon recommends. “In this way you will be expressing a healthy human impulse, namely, to integrate yourself into the larger systems in which you are embedded.”

Read the rest of Kaufman's seven rules for happiness at Scientific American