Ever notice how, once you hear a really great idea, you start to hear it everywhere?

I hitched a ride with Southwest from St. Louis to Baltimore the other day. My mission: to present a live webcast based on the leadership lessons found in my book Look, Lead, Love, Learn. Part of that presentation examined some of the insights I learned from a recent keynote presentation by Tim Sanders, a former Yahoo! executive and best-selling author of such fantastic books as Love Is The Killer App, The Likeability Factor, and Today We Are Rich (which should be required reading for all businesses, in my opinion). Sanders’ key message boiled down to this:

Relationships matter.

Check that. Relationships don’t simply matter; they might be the only things that matter.

“Your network defines your net worth,” Sanders said during his keynote at a recent CCH User Conference. “Relationship quality is everything.”

He went deeper than that, of course, focusing on the importance of company culture and qualities like friendliness, generosity, and empathy. But those are all merely the fuel that drives our relationships. In the end, Sanders says, our bottom lines depend on the quality of our relationships with others.

I relayed this story, and others like it, to our webcast audience, then wrapped up the session and ducked into a meeting with the MACPA’s communications crew. Among them was Greg Rittler, who heads up Blue Ocean Ideas, the creative and marketing force behind the MACPA and the Business Learning Institute. During the meeting, Greg told us of a blog post his wife, Elise, had written recently about the Harvard Grant Study. This groundbreaking study focused on the quality of life of 268 Harvard sophomores from the classes of 1939-44. The study followed these folks for an astounding 75 years, making it the longest longitudinal study ever.

The results of the study offered remarkable insights into the values that bring true happiness to one’s life. Here are some key findings from the study, courtesy of Huffington Post senior writer Carolyn Gregoire. See if these don’t sound familiar:

1. Love is really all that matters “It may seem obvious, but that doesn’t make it any less true: Love is key to a happy and fulfilling life. … (Harvard psychologist George) Vaillant has said that the study's most important finding is that the only thing that matters in life is relationships. A man could have a successful career, money and good physical health, but without supportive, loving relationships, he wouldn't be happy.”

2. It’s about more than money and power “We found that contentment in the late 70s was not even suggestively associated with parental social class or even the man’s own income," Vaillant told Gregoire. "In terms of achievement, the only thing that matters is that you be content at your work.”

3. We can all become happier “A man named Godfrey Minot Camille went into the Grant Study with fairly bleak prospects for life satisfaction,” Gregoire writes. “But at the end of his life, he was one of the happiest. Why? As Vaillant explains, ‘He spent his life searching for love.’”

4. Connection is crucial "The study found strong relationships to be far and away the strongest predictor of life satisfaction,” Gregoire writes. “And in terms of career satisfaction, feeling connected to one's work was far more important than making money or achieving traditional success.”

See what I mean? If you don’t believe Tim Sanders, you at least have to give lip service to the longest longitudinal study in history: Relationships are vitally important, not only to our bottom lines, but especially to our future states of mind.

The final word? All business — the business of growth, of profit, of personal development and satisfaction, of happiness — is social in nature. That only makes sense. We are social creatures, after all. The better we are at connecting with others, the happier and more fulfilling our lives will become.

It’s a social world … but that’s nothing new. It always has been. We’re now beginning to realize the benefits of mining those relationships.