IEX CEO Brad Katsuyama shares the 'critical' piece of advice he gives other entrepreneurs about getting through rough patches

Business Insider/Jessica Tyler

"You have to have a core belief that what you're trying to do is real," said Brad Katsuyama, pictured.

• Brad Katsuyama, CEO of IEX and the star of Michael Lewis book "Flash Boys," spoke on Tuesday at Business Insider's IGNITION 2018 conference.
• Katsuyama said successful entrepreneurship means having experienced the problems you're trying to solve.
• He was a trader for years and felt there was a need for an alternative exchange that would prevent predatory trading.
• Katsuyama said, "In the lowest possible moments, where possibly you're even doubting yourself, you have to have a core belief that what you're trying to do is real."

Brad Katsuyama has one "critical" piece of advice for other entrepreneurs: "You have to have experienced the problems that you're trying to solve."

Katsuyama is the CEO of upstart stock exchange IEX, and is best known as the star of Michael Lewis' 2014 bestseller, "Flash Boys."

At Business Insider's IGNITION conference in New York Tuesday, Katsuyama said, "If you're doing something controversial, there's going to be a lot of people fighting against you. In the lowest possible moments, where possibly you're even doubting yourself, you have to have a core belief that what you're trying to do is real. It's a problem that needs to be solved."

Katsuyama added, "When your back's against the wall, you have to firmly believe that, or you're never going to make it through."

IEX was born out of Katsuyama's experience as a trader at Royal Bank of Canada: He founded the company in 2012 as a new exchange that would prevent the predatory trading that took place on traditional US exchanges.

In September 2018, IEX snagged its first listing from Nasdaq, Business Insider's Frank Chaparro reported.

"I lived the story," Katsuyama said of the "Flash Boys" plot. "Never for a second have I doubted what I lived through."

Katsuyama's memory of his experiences as a trader kept him going through the ups and downs of launching IEX.

Read more: IEX CEO Brad Katsuyama talks about life after 'Flash Boys' and how he's taking on the New York Stock Exchange and Nasdaq

Some other successful entrepreneurs have similar advice. Neil Blumenthal, CEO of Warby Parker said the best way to discover a solid business idea is to write down your frustrations every day.

Interestingly, Blumenthal also said that many entrepreneurs "needed to live a little and experience a little bit of life to identify where there are problems that need solving."

As for Katsuyama, he said, "At the end of the day, when no one believes in your idea, you have to be the one who believes in it."