This is the most important lesson from the longest-running study on happiness!

We humans are complicated. And happiness is one of the most complex emotions we experience. Our life is often an effort to reveal its meaning. Everyone has their own definition of happiness. We live, grow and evolve and so our definition of happiness changes.

Researchers from Harvard Medical School have analyzed gigabytes of scientific data to find out what really makes people happy.

Harvard began this research in 1938 and today it is more than 80 years old. Lead her dr. Robert Waldinger, professor at Harvard Medical School, who is the fourth director of this study.

Over the course of 75 years, they followed the lives of 724 men year after year, documenting their careers, personal lives and health. No one knew how these men's lives would turn out. The participants, all teenagers at the time, went through countless career paths – from factory workers and lawyers to masons and doctors. One even became president of the United States.

To collect authentic data, academics designed detailed questionnaires and supplemented them with intimate interviews with participants in their living rooms. They also collected the men's medical records, examined their brains and interviewed their children and wives. They occasionally recorded conversations between them and their wives.

Based on thousands of pages of information read, the team provided some simple yet powerful lessons for a happy and fulfilled life.

Being actually connected to our loved ones is a blessing

Which moments of your life do you cherish the most in nostalgic memories? What memories bring a smile to your face? People who are more connected to family, friends, community are happier, healthier and live longer than people who are less connected.

The study also looked at the other extreme; an example of complete loneliness in relationships. She found that people who were more isolated from others were less happy, less healthy in middle age and had shorter lives.

Another lesson: People who were most satisfied in their relationships in their 50s were the healthiest in their 80s, according to a study. Conflicts in the marital relationship had a long-term effect on the health of these people more than divorce. How connected you are and how safe you feel with your family is more important than how many people you are in contact with.

Good relationships are not always smooth sailing

We often imagine that good relationships are always smooth sailing. This is neither necessary nor practical. It's okay to argue every now and then. Treat fights like muscle training. You will have some bad days, but as long as you consistently work on your relationships, there will be no problems. This will help you resolve conflict situations more easily.

Researchers have indicated that some couples argue on a daily basis. However, none of these arguments affected their lives because they knew they would always have each other's backs during crises.

Good relationships improve memory and creativity

Happiness is not the only child of good relationships. Those with long-term relationships had a sharp memory even at 80, but those who could not count on their loved ones experienced memory decline earlier, as confirmed by brain scans.

Stress has been a major cause of many brain-related problems, and this study reaffirms that correlation.

"In the end, only three things matter: how much you loved, how gently you lived, and how gracefully you let go of things that weren't meant for you." – Buddha

Relationships can be messy and complicated, and it takes hard work to maintain them. And this work lasts a lifetime. It never ends. Working on relationships rarely brings instant gratification.

You can always call your old friend tomorrow, or the day after, or the day after that... But you can choose to do it now. Consider replacing screen time with family time, taking up a new and fun hobby together, or going for a long walk.

"Life is short: break the rules, forgive quickly, kiss slowly, love truly, laugh uncontrollably and never regret what makes you smile." – Mark Twain