No matter how talented or intelligent you are, many of the greatest lessons—in business and in life—don’t come until after years of experience.

Oftentimes, when looking back, these are the lessons the most successful people wish they knew when they were in their 20s. Other times, they're glad they didn't know them, as knowledge sometimes hold us back in the wrong ways.

From discovering just how much competition kills creativity to the tests that leadership often brings, below, nine executives share the lessons they learned in retrospect after years of doing business and leading teams.

LESSON NO. 1: JUST BECAUSE YOU START A COMPANY OR LEAD A COMPANY DOESN'T MEAN YOU ARE A LEADER

Julia Hartz, cofounder of Eventbrite

"I've learned in the last year that if you can't see it, you can't be it," says Hartz. In other words, "there is no finish line to leadership." You’re tested repeatedly on your ability to lead others and form allies.

Hartz adds: "It's something that you work on and earn over and over again. For example, female leaders in tech today are helping shape the greatest generation of women entrepreneurs through empowerment and modeling. Strong modeling has the ability to shape the next generation, and I believe we’ve come a long way."

LESSON NO. 2: COMPETITION KILLS CREATIVITY

Philippe von Borries, cofounder of Refinery29

In the business world, you’re constantly facing competition. To succeed, you have to 
know the ins and outs of the competitive landscape, recognize marketplace dynamics, understand how your competitors do business, yet still stay true to your brand.

"As a creative business at heart, I’ve seen dozens of times how competition kills creativity," says Von Borries. "I’ve witnessed myself doing this before . . . referring to X and Y brand doing something new, and all of a sudden, the room freezes over. When you go into comparing and contrasting, you don’t have creativity any more. You’re only creating a different, maybe worse, version of your competition. It’s a zero sum game.

"Once you follow the competition, you disconnect from what you’re actually great at. Being creative means creating something out of nothing. Never tolerate comparing and contrasting."

LESSON NO. 3: THINK ABOUT IMPORTANT DECISIONS FOR A DAY OR TWO BEFORE ACTING

Chet Kapoor, CEO of Apigee

"Over the years, I've gained a tremendous amount of respect for the power of patience," Kapoor says.

"When I was a young professional, I believed the most important characteristics of a successful leader were talent and discipline—and that was pretty much it. I thought that if you have talent and you put in the discipline—whatever your equivalent of 10,000 hours would be—you are equipped for leadership," he explains.

"But I understand now that making important decisions, a defining responsibility of any leader, sometimes requires patience. If I'm not comfortable with a big decision now, I wait a day or two. I don't use this time to gather more data, a timeline, or create a list of pros and cons. I just give the decision the gift of time. Often with a little time and patience, the decision will manifest itself clearly."

LESSON NO. 4: BEING NAIVE IN BUSINESS IS A GOOD THING

Jill Salzman, founder of The Founding Moms

Looking back, Salzman says she knew nothing about building a business. Today, she's built three.

"What I didn’t know actually helped to pave a way of running a company the way I need to do it, not the way others have done it before," she says. "That may have come at some expenses, but the gains have been tremendous."

She adds: "When I meet twentysomethings now who clearly don’t know what they’re doing, I applaud them and help steer them in a slightly more helpful direction. But we entrepreneurs need to figure it out on our own, that’s for sure."

One specific experience that taught Salzman this lesson was when The Founding Moms discovered that its meetup, the Founding Moms’ Exchanges, was growing quickly. Everyone told Salzman to keep it small so that she can "get it right." Instead, she pushed for expansion and today, Founding Moms’ Exchanges exist in 47 cities in 10 countries.

"If I were wiser, I would have listened," she says.

LESSON NO. 5: LET YOUR CUSTOMERS INFLUENCE YOUR PRODUCT

Brett Northart, cofounder of LE TOTE

When Northart and his cofounder, Rakesh Tondon, started LE TOTE, they started small and used feedback from their customers to change and develop the product.

"If we had over-optimized the product early, we would have built an entirely wrong product for the wrong customer," says Northart. "A lot of people assume they know everything when they are first starting out, but you have to remember to listen to your customers and have a genuine curiosity to keep learning. Otherwise, your product or company will never grow."

LESSON NO. 6: DON’T AVOID THE BIGGER GOALS AND PROJECTS

Andrea Cutright, COO of Ask.fm

As a leader, you’ll have to make a lot of decisions. Don’t make choices that fail to make an impact, advises Cutright.

"The startup world forces you to prioritize given limited resources and the high demand to constantly deliver," she says. "You can’t hide behind the work that doesn’t move the needle."

"Even now, when I have more resources with a larger company, the same principles apply. I make my expectations known and communicate them clearly and effectively with my teams, and those I work with. I only check emails in the morning and at the end of the day, and spend the bulk of my time actually working on the most important priorities. But my team knows, if something new is pressing and important, they have my attention."

LESSON NO. 7: ALLOW YOUR TEAM TIME TO COME UP WITH THEIR OWN IDEAS

Yee Lee, cofounder of Vouch

"The easy and short-term effective leadership style is to be the person who always has answers and ideas," says Lee. "It's much harder, but more empowering for your team, to hold your tongue on your own ideas and keep asking questions until your team comes up with answers themselves."

LESSON NO. 8: YOU ARE MADE UP OF YOUR ACTIONS

Dan Rosensweig, CEO of Chegg and former COO of Yahoo

When things go wrong, it’s easy to protect yourself and blame some other force.

"I was having one of ‘woe is me/it’s not my fault’ moments, when Bill Campbell [chairman of Intuit] called and asked me to take a walk with him ‘to the woodshed,’" says Rosensweig. "He told me, ‘Take responsibility for your own life, and own your outcome.’"

"Ultimately, it taught me you are what your record says you are," he continues. "When things aren’t going well, that’s the time to apply everything you’ve ever known and learn to drive through the problem, not be consumed by the problem."

LESSON NO. 9: DON’T MAKE PROMISES THAT YOU CAN’T KEEP

René Lacerte, CEO of Bill.com

"It is never good to oversell a customer, and it is disastrous to oversell an employee—whether you are recruiting them or enticing them to stay," says Lacerte. "When it comes to people, you must make sure folks want to come or stay for the right reasons, and not just for a polished sales pitch.

"I learned the hard way a few times that the most important person to do the selling on working at your company is the employee themselves, not you. When you get that right, you'll have an easy time focusing on what makes the talent you already have happy, and that in turn attracts and leads to more great talent."