7 of the best pieces of advice self-made millionaires shared about money in 2018

The power of compounding is endlessly emphasized, and even Reddit cofounder Alexis Ohanian attests to it, along with the benefits of delayed gratification.

"The miracle of compounding is real," he told MarketWatch in an interview when speaking of the best financial advice he's received. "It's important to have a long-term focus when it comes to investing and saving. Generally speaking, the better you are at delaying gratification and the overall happiness of spending, the better off you'll be with your long-term financial well-being."

He added: "The marshmallow test [an experiment in the late 1960s to see how long children could delay gratification] was apparently pretty flawed and didn't control for lower income kids who have different levels of food insecurity than wealthier kids, but I think there's some fundamental value to being able to delay gratification, especially from a financial perspective."

Grant Sabatier of Millennial Money retired early at 30 years old as a millionaire. During early retirement, he's realized that success doesn't come from achieving financial independence or external factors.

"On my own journey I've learned that success doesn't come from money, or a promotion, or the next big project, or that new car," he wrote. "It doesn't come from outside. It comes from within."

Now that money is no longer his goal, he realized how unimportant it actually is.

"To me, success isn't about money, it's about peace," he wrote.

"I just want to feel a peace. I want to feel calm and present. I want to feel alive. I want to feel at one with the world and myself. I don't want to be shackled by worry about money or the future. I want to feel at ease. Like I've found my rhythm. Like I'm in the right place. That 'peaceful easy feeling.'"

Wealth coach and lawyer Adeola Omole went from $70,000 in debt to a seven-figure net worth by living by her mantra: "Spend passion, cut junk."

"In a nutshell, it means that you need to start spending your money on things that bring you joy and that you are passionate about," Omole previously told Business Insider. For example, she spends her money on books and investing; others may put their money toward travel.

"You need to do everything in your power to stop spending your money on things that don't bring you joy, things that you're not passionate about, and things that don't add value to your life," Omole said.

For Omole, this "money philosophy," as she calls it, has done more than help her crush debt and build wealth — it's changed her outlook on money.

"Once I stopped associating money with consumption and started associating money with options, my relationship with money changed from being based out of fear to now being a source of empowerment," Omole said.

Actress Melissa McCarthy told Glamour magazine that having a strong business sense and negotiation skills are vital to making more money, Insider reported.

"It's like this: You can stay in a local theater and work for the art of it, and that's great," she said. "Or you can say, 'I can make this my business.' And if you want to do your business well, you'd better learn how to handle those negotiations, how and when to push, and when to lay off."

It's a lesson she's trying to pass on to her daughters, who enjoy making slime.

"My oldest daughter wants to start selling it. I was like, 'Great. Start a business,'" McCarthy says. "It can't just be 'gimme, gimme, gimme.' I talk a lot about, 'We work hard for things.'"

In an interview with personal-finance blog Grow from Acorns, self-made millionaire and best selling author David Bach his top investing advice.

It boils down to this: Diversify your investments, but keep it boring.

"Have a diversified portfolio with stocks and bonds. When it comes to your money, boring is really good," he said.

"Most people don't have someone who pushes on them. Often decades go by before they realize it's time to get serious with their money," he said. "If you can get young people to save and invest early on, their whole life will be different."

In a post for Business Insider, Ramit Sethi, author of "I Will Teach You To Be Rich," wrote that we don't think we can earn money because no one teaches us how.

"We never see people like us do it, so we have no reason to believe we can," he wrote.

He added: "We're left with a deep-rooted, toxic belief that earning more is only for 'other' people. Then tell ourselves things like, 'I can't earn more, I don't have time/an idea/the right background.'"

He called this a self-limiting belief — but once you realize it's not a fact, he said, you can get started earning more money.

He broke it down with simple math: If you make $50 per hour, work 10 hours per week for five months, you could earn an extra $10,000. To earn that in two-and-a-half months, you'd have to make $100 per hour at 10 hours per week.

"Whether you actually make $50 per hour is beside the point," he said. "The real message is this: If goals seem too out-of-reach, we're not able to visualize what to do. Instead, dream big, start small."