5 successful entrepreneurs share the most important lesson they learned in their 30s

Blumenthal and Gilboa cofounded hip, affordable eyeglasses retailer Warby Parker with Andrew Hunt and Jeffrey Raider in 2010. Last June, the company sold its millionth pair of glasses and is now expanding its brick-and-mortar business in addition to the ecommerce model that made it famous.

Blumenthal and Gilboa agree that as they learned to develop a business, they learned how to gain an advantage over once-intimidating competitors.

“Everything is not what it seems,” they say. “Peek behind the curtain at a bunch of organizations, and it’s not as tightly organized or well-run as you’d expect. There’s so much opportunity for people to be more thoughtful. Being thoughtful and deliberate in one’s approach is a big competitive advantage. The most thoughtful company wins.”

The billionaire investor made the biggest deal of his life when he sold his company Broadcast.com to Yahoo for $5.7 billion in Yahoo stock in 1999.

In his career, he’s made over 120 investments in both major institutions like the Dallas Mavericks professional basketball team and startups featured on “Shark Tank.” As he became a savvy investor through trial-and-error, he realized that any company, regardless of management issues, can be made to scale if they’ve developed an audience.

“In my 30s, I learned that in a business sales cures all,” he says. “If you can generate sales you can have a succesful company.”

Roth founded Matisia Consultants in Seattle in 2006. Her firm has worked with several Fortune 100 companies, and last year it brought in over $60 million in revenue. Roth recently opened an office in Los Angeles and is planning an expansion into San Francisco.

In her 30s, she realized that it’s a sign of strength, not weakness, to utilize your support group.

“I learned to be a bolder version of me, with more power to run the marathon of life, see the big picture, and stop from time to time to get the water somebody is offering you during this marathon,” she says. “Say ‘thank you,’ recognize it’s a team effort, but continue running and pushing a little more.”

Lubetzky founded all-natural energy bar brand KIND in 2003 as a subsidiary of his company Peaceworks, which is dedicated to fostering business relationships between entrepreneurs from conflicted groups. He spun off KIND as its own company in 2009 and achieved rapid growth, which he details in his upcoming book “Do the KIND Thing.” It brought in approximately $197 million in revenue in 2013.

“In my 30s, I was working relentlessly to grow KIND, and the mistakes I made could fill a business school course on how not to run your startup. But I eventually learned to be comfortable with failure,” Lubetzky says.

“Trying to forget or hide your mistakes is a huge error. Rather, hold them near and dear to your heart. Wear them proudly,” he says. “Failure holds the seeds for greatness. So long as you water those seeds with introspection and are open to learning from them, they can be the root of your success.”

In 2008, Doane created Raintees, an apparel line that plants a tree in an endangered rainforest for every shirt sold and donates school supplies to a child in need for every tote bag sold. Raintees works with nonprofits in over 20 countries.

Doane noticed in her 30s that people used their careers to pursue promotions and notoriety without being grounded in anything.

“The most important lesson I learned in my 30s is that everyone just wants to be happy, but most people have no idea how to be, so they spend a long time chasing all the wrong things,” she says. “Real happiness lies in the small things: good books, a meal with friends, and having a purpose greater than yourself. I am spending a lot more time focusing on the simple things in my 30s.”