Since co-founding Whole Foods Market, John Mackey has had four decades for the success to go to his head.

But as he expanded his enterprise to 500 locations in North America, employing more than 90,000 people, and then sold to Amazon in 2017 for more than $13 billion, he's focused part of his energy on refusing to let his ego swell.

Over the years, he's seen peers let their corporate power influence their self-worth. "Entrepreneurs, particularly entrepreneurs that get a little bit successful, their narcissism can get out of check and they begin thinking they're some kind of genius," he says on Inc.'s What I Know podcast.

Success isn't destined to poison, Mackey notes: "It all depends on how you react to it." He reins in his ego by disassociating money with happiness, by leaning on gratitude, and by refusing to let success get in the way of nurturing his personal relationships.

Realize Money Isn't a Happiness Engine

Mackey is worth an estimated $75 million. He flies commercial and for years drove a Honda Civic hybrid. "No matter how rich you are, no matter how successful you are, it's all going to be left behind. And what really matters in life is relationships, love, friends, family. That's what's really important," he says. Mackey in 2006 made public how he decided to walk that walk: Like many other execs, he set his own salary at $1; unlike so many of them, he also refused any future offer of bonuses or stock, a common method of skirting c-suite salary limits.

Instead, relationships give you the greatest potential for happiness. As Mackey, who's been married almost 30 years and who credits his wife with teaching him the importance of relationships, says:

When we're on our death beds...we won't be regretting we didn't work harder or we didn't make more. We'll be regretting what we didn't say to our parents or we didn't say to our children--or we didn't express enough love to our friend... that's what we'll remember because that's what's really most important in life. And if we remember that as we go through to business, as we go through our work, in our challenges and our success, we have a good chance to be happy.

Keep Friends Close, and Use Them for Frequent Reality Checks

 It's not just family who need your love; it's friends. And true friends, Mackey says, are the ones who will call you when you've changed.

"Friends are people that will tell you when you're in your ego, when you're making mistakes, when you are not acting as a leader, not acting as a servant leader to others, that you're on some kind of ego trip," Mackey says. "You need people to tell you that." 

Make Room in Business for Gratitude

In order to keep your vanity, your pride, and your ego from inflating when times are good, Mackey says, "you always have to realize how fortunate you are." Expressing gratitude frequently not only helps to ground you, but also can help infuse your organization with goodwill toward others, Mackey says.

"At Whole Foods, we end all of our meetings with appreciations and they're voluntary. Nobody has to do it," he says. Employees could speak up to say thanks to colleagues for help they'd received over recent days--or to applaud another's job well done. Even the board of directors used this practice at Whole Foods, right up until the Amazon acquisition, he says. And the simple optional practice seemed to nurture team unity. "When people are really appreciating each other and it's authentic, that helps the team and helps a group bond together. It builds trust."

Listen to the full episode in the player below, or anywhere you get your podcasts.