When the video of Brené Brown delivering a compelling, earnest, and vulnerable TEDx talk was put online in late 2010, it didn't take long to go viral. Brown, a professor, author, and public speaker, was both humbled and terrified. And as the video circulated online, she made the crucial misstep of ignoring the first rule of posting something heartfelt online: Don't read the comments.

She read the comments. "The truth is, those comments hurt. They hurt me. They hurt my feelings," Brown said. Her talk on courage and vulnerability opened up Thursday's Inc. 5000 conference in a packed ballroom in Phoenix.

Brown recounted doing the TEDx talk, and knowing that she put herself out there for everyone to see--making herself vulnerable in doing so. "If you decide to live in the arena, you will get your ass kicked," was her takeaway. "You can choose comfort, or you can choose courage, but you can't have both."

She's since delivered another TED talk (this one got 17 million views online), and has published a renowned book on courage--and the vulnerability it requires to be truly courageous--called Daring Greatly. In it, and in her speech Thursday, Brown dispels a host of myths about vulnerability that her research has illuminated, and cracks open some truths about how we humans connect with one another.

Let's rewind to Brown's reaction to reading those online comments to her widely watched TEDx talk. She could have just tuned them out, she realized.

"At first I considered the 'I don't give a shit' option," she said. But she realized taking that approach would be irresponsible to her own emotions. And it completely ignored human vulnerability--a concept she'd been researching. "The minute you stop caring what people think, you lose capacity--you lose capacity to be vulnerable."

She'd entered the arena, and wasn't willing to step back out into a place of weakness. And here's where vulnerability is tied to leadership.

"People are confused about what is vulnerability and what isn't," Brown says. "Having the courage to show up and be seen and put yourself out there when you have no control over the situation: That's vulnerability. Vulnerability is the absolute prerequisite for badassery."

That's because if you're going to be brave, you're going to get hurt.

"Vulnerability feels terrifying, and like it could be costly," Brown says. "But its never going to be as costly as getting to the end of your life and thinking 'what if I would have shown up?'"