Thinking like a child means being open, excited and optimistic. It also means dreaming big.
These four savvy, successful entrepreneurs are teens and tweens, but they set big goals for themselves and keep achieving. Here are five of the most important lessons they feel like they've learned along the way.
Lesson 1: Keep on top of your finances with automated technology
"I am a Generation-Z kid and I love technology. I would say, track your numbers through a piece of technology, whether it's a laptop or a phone that you can pull out whenever you need to," Ulmer tells CNBC.
Lesson 2: Turn lemons into, well, lemonade
When Ulmer was four years old, she was stung by two bees within a week. She was upset but, at her parents' urging, she learned about bees and why they are important. That research inspired her to start her drink business, Me & the Bees Lemonade. Ten percent of profits go to charities including Heifer International, the National Park Services and the Sustainable Food Center of Austin.
"Dream big, and not only dream big, but also dream like a kid," says Ulmer. "When a kid has a dream and they want it to come true, they will do whatever it takes to do so. They don't see the obstacles in the way, they will just fight hard to make it come true.
"Sometimes you have to get into that mindset and dream like a kid," she says. It will "put you into a better goal setting stage for your business."
Lesson 3: Know your worth
Taylor Rosenthal, a high-schooler grader from Opelika, Alabama, launched RecMed, whose vending machines dispense first-aid products. He got an offer to sell his company for $30 million from an undisclosed bidder but the young entrepreneur didn't think it was enough money.
"At the time, I felt the deal wasn't right — I felt like I wanted to grow and develop the company from what it was, which drove me to turn it down," he says.
As of last year, Rosenthal was "hopeful" he could close a deal to sell his company for $50 million.
Lesson 4: Start preparing early to accomplish big goals
Sixth-grader Micah Amezquita started a trash-can toting business in his neighborhood to raise money for college so he can become an aeronautical engineer. When his father posted about his son's business on LinkedIn, the post went viral.
I "have a lot of things I'd like to do when I'm bigger, so I definitely have to go to college to do those things," says Amezquita. And he keeps a positive attitude through the grunt work. "I like the job!" he says. "There's nothing I don't like about it."
Lesson 5: Don't let doubters slow you down
Benjamin "Kickz" Kapelushnik is still in high school, but the teen entrepreneur expects his sneaker business to hit $1,000,000 in annual sales. Known as the "Sneaker Don," Kapelushnik started selling sneakers to friends in the fourth grade.
Now he aims higher. The most expensive pair of sneakers he has ever sold went for $20,000 and his client roster includes Odell Beckham Jr. and DJ Khaled.
"When I was in 8th grade I bought a shoe for $800 and my dad told me that I am out of my mind and that I would lose money. Then I wore it and sold it for more. My mom was always with it but my dad has come around," he tells CNBC.