The skills that can make you highly successful aren't necessarily innate. You can practice them, and get better at them.

That's according to bestselling authors and leadership researchers Brené Brown and Simon Sinek, who sat down with Wharton organizational psychologist Adam Grant for a recent episode of his "ReThinking" podcast.

"They're skills that are observable, measurable, teachable — we can practice them," Brown said.

Specifically, Sinek and Brown highlighted three soft skills that highly successful people tend to share:

1. Public speaking
2. Boundary setting
3. Vulnerability

Cultivating these skills can be tough. If they don't come naturally to you, it means getting out of your comfort zone and opening yourself up to external judgment.

Here's how to practice them as comfortably as you can, according to Brown and Sinek.

Public speaking

Public speaking can help boost your confidence levels and leadership skills, according to Stanford University Graduate School of Business organizational behavior lecturer Matt Abrahams, who referenced a corporate study of more than 100,000 professional presentations in a 2016 university blog post.

But it's one of the most anxiety-inducing workplace skills of them all: 15% to 30% of people actively fear it, found a 2016 study published in the Journal of Graduate Medical Education.

Even for Sinek, who's delivered multiple TED Talks, public speaking and communicating effectively with others can be hard. His solution is more physical than mental, he said.

"There's a physiological connection between our hands and how fast we talk," said Sinek. "I talk very fast and I move my hands a lot. If I'm with other people that speak fast and move their hands, it's all good ... If I'm in a meeting with somebody who is slower, they think before they speak, what I've learned to do is to interlock my fingers and to hold my hands still."

Holding his hands closed helps him speak more slowly without devoting too much focus to it, allowing him to instead pay more attention to the conversation, he said.

"This wonderful physiological connection has really helped me be heard and understood by people who think [differently] than I do," Sinek said.

Boundary setting

When you're engaged at work, your work often turns out better. But it's hard to be enthusiastic about any given project when you're dealing with life's stressors, and even harder when other people are constantly confiding in you about theirs.

Empathy is an important soft skill in the workplace, but "you can't give what you don't have," Brown said.

"You've got to set boundaries, and you've got to model boundaries," she said. "I would dig into ... why are you taking care of other folks' s---? Is that where you think you have value?"

The first step to setting boundaries, especially when you're trying to protect your mental health: Figuring out what you need or want to get from any given conversation, New York-based psychologist Shaakira Haywood Stewart told CNBC Make It in 2021.

Then, tell your colleagues what you are and aren't willing to work on, and offer solutions for any potential problems that might arise from your boundary-setting.

"It's hard to not respect someone who's coming with information, suggestions and not complaining," added Debra Kissen, the clinical director of Chicago-based cognitive behavioral therapy treatment center Light on Anxiety.

Vulnerability

A lot of Brown's research centers around the concept of showcasing vulnerability in the workplace. It pushes you to "show up and put yourself out there to be all in, when you don't have any control over how it's going to go," she told NBC's "Today Show" in 2019.

To her, that doesn't mean dishing your personal business to managers or colleagues. Rather, it means being transparent about circumstances that may hinder your performance or morale.

Maybe you don't know how to use a new piece of software, or you're dealing with a family issue that's distracting you. Be forthcoming about these situations, Brown recommends. 

"It takes a tremendous amount of courage" to open up when things are hard, she said on Grant's podcast — but doing so is a sign of strength, not weakness.

"You can say, "I'm really struggling right now. I've got some stuff going on and it's hard, and I wanted y'all to know," Brown told the TED podcast WorkLife in 2021. "And I want you to know what support looks like for me is that I'll check in with you if I need something or I may take some time off."

Correction: This story has been updated to reflect that a 2016 study on fear of public speaking was published in the Journal of Graduate Medical Education.

Disclosure: NBC and CNBC are divisions of NBCUniversal.

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