Happy relationships shouldn't be hard work! That's one of the upbeat findings from my landmark study of marriage, which has been following 373 married couples since 1986.[1] Here's more good news for lovebirds: If you're in a happy partnership, married or not, you can keep it that way or make it even better by introducing a few new behaviors and small changes into the relationship. While many relationship experts say you need to focus on fixing what's wrong, my research shows that adding positive behaviors to the relationship has a much greater impact on couples' happiness. 

1. Accept your partner's uniqueness. We have all had moments when we wished our partner was thinner, wealthier, more romantic, and so on. Take a look at your expectations and ask yourself how realistic they are. Unrealistic expectations lead to chronic frustration, which my study found is the main reason relationships fail.

2. Do random acts of kindness -- often. Small gestures that say "I'm thinking of you" are essential to keep the relationship bond strong -- e.g., he fills up her tank with gas, she brings him a steaming cup of coffee in bed. Hand holding, touching or a midday love email are all small ways of showing affection. Research shows that the accumulation of small gestures has a bigger impact on couple happiness than grand, less frequent gestures.

3. Devote 10 minutes a day to connecting. Most couples think they talk to each other all the time. But how often do you talk about things that really deepen your understanding of your mate? The happy couples in my study talked to each other frequently -- not about their relationship, but about other things -- and felt they knew a lot about their spouse in four key areas: friends, stressors, life dreams, and values. Set aside 10 minutes a day -- I call it "The 10-Minute Rule," to talk to your partner about anything other than work, family, the household, or the relationship. This simple change infuses relationships with new spirit and life.

4. Fall in love all over again -- weekly. Spontaneous dates are great, but the truth is that we're busy and we often don't make time for our lover. Keep your love relationship healthy with a once-a-week date -- dinner out, a movie, dancing, an art show, couples yoga -- whatever. Take turns planning it. Men: studies show that women are more passionate and their libido is stronger when they are out of their home setting--away from kids and chores. Watch what happens when you book a night at the local hotel, and get a friend or relative to watch the kids and pets.

5. Change and grow -- together. Your love relationship is a living thing that needs nourishment to grow and develop. The best way to nurture it is to infuse it with change. Much like fertilizer for a plant, introducing change into relationships has been shown to be a key ingredient to couple happiness. The changes can be small, but they have to upset the routine enough to make him or her sit up and take notice. Switch roles: If he always makes the dinner reservation, let her do it. Or interrupt routines: Play hooky from work and do something fun together, like visiting a museum or tourist spot nearby. Or try something new: Take a water-skiing class together, or go on a mediation retreat.

6. Get to know each other's friends and family. My research found that men, in particular, are happier when the female has a good relationship with his family. Also, couples who accept -- not necessarily love -- each other's friends and make an effort to know them report being happier than couples who have separate friends and separate family lives.

7. Be a caregiver. One of the three things couples need for a happy relationship is support (the other two needs are reassurance and intimacy). The happy couples in my study uniformly said that having a partner who was "there for them" was one of the most important aspects of their relationship. Men often like to give instrumental support -- the kind of support that fixes or solves a problem. Women often like to give emotional support -- empathetic listening and constructive feedback. Find out what type of help your partner really wants first, and then give it to him or her -- often and consistently.

8. Keep it light -- and full of light. Laughter is a spiritual practice. In marriage, it acts as happiness medicine. To keep your relationship from slipping into a rut, you need to balance the rational aspects of your partnership with the fun parts. Yes, you need to do certain things to keep your life orderly and your partnership secure. But don't forget to play. Try to rediscover the pure delight of playing a game, acting childish in the snow, watching a silly movie, dragging her onto the dance floor, and so on.

9. Find a healthy way to communicate. The happy couples from my long-term study of marriage all said that good communication skills were what kept them together and thriving. This means not only asking your partner what he or she needs, but telling your partner what you need. It means checking in regularly to find out what stressors are rearing their ugly head in your partner's life, and it means learning how to fight fair -- no name calling, shaming, or kitchen sinking (bringing up everything that's bothered you for the last year).