Barbara Corcoran says standing up to Donald Trump 30 years ago was a pivotal moment in her life

Barbara Corcoran and Donald Trump have had a rocky history - including lawsuits  - but Corcoran fondly remembers the time she met Trump.

Corcoran, now best known as one of the stars of "Shark Tank," built her fortune and reputation with the Corcoran Group, which she established as one of New York's premiere real estate firms.

In 1983, Trump oversaw the completion of Trump Tower in Manhattan, and had established himself as a force in the industry. Corcoran, who was 34, was intimidated by him.

She recently stopped by Business Insider's New York office for a Facebook Live Q&A, and though she didn't want to get into politics, she brought up a story about the Republican presidential nominee when a viewer asked how to deal with fear of failure.

"I still doubt myself. I'm ashamed to admit that after all these years," Corcoran said. But when she's afraid, a "tape reel" starts playing in her head, drowning out a negative inner monologue. While she may be best known for the way she freely speaks her mind, she said that in her 20s and early 30s she was very insecure.

A turning point came in the early '80s, when Corcoran notified Trump that his Trump Tower residential properties, which he was advertising as the most expensive condominiums in the world (this was back when such a claim was appealing), were actually in the bottom tier of the top-10-most-expensive list she was about to publish. As soon as he got the message, he called her to his penthouse office.

"I was scared to death in that mirrored elevator going to the top floor of Trump Tower," Corcoran said. "Thinking that bad voice: 'Oh, my God, what did I do this for? I'm in hot water. What am I going to do?'"

She willed herself off the elevator and stepped into his office, into a small chair that seemed to shrink beneath his giant desk.

Trump was furious, she recalled, and he was yelling and gesturing wildly. Mid rant, "all of a sudden I got the first inkling of that tape: 'Oh, yeah? You're not talking to me like that,'" she said.

"One of the most memorable and treasured moments of my life - it sounds so stupid how you treasure these things - but was when I got up out of that mini chair he stuck me in, went over to his side of the desk and had the courage to put my hand on his shoulder and look over his shoulder."

Trump was thrown off, she remembered, and the power dynamic shifted into her favor. She presented an idea to him: If she changed the way she was measuring "most expensive" (she couldn't remember the specifics, but it was something like price-per-room versus price-per-square-foot), then Trump could rightfully take the No. 1 spot he so desperately wanted.

They agreed to a deal where Trump would be able to advertise his properties with this tagline as long as he included the Corcoran Group's branding on all advertising.

"I got paid very well for finding the voice and the courage within me that day, and I've been practicing it ever since," Corcoran said.

Watch the full Facebook Live Q&A: