The No. 1 trait you need to be more successful than most, says workplace expert: It's 'the single most important differentiator'

Confidence really does breed success, according to a workplace and leadership expert.

It's the key to making "very impactful decisions" in the workplace, even under pressure, says Bonnie Low-Kramen, author of "Staff Matters: People-Focused Solutions for the Ultimate New Workplace."

The soft skill has helped boost the career of many of today's successful leaders, Low-Kramen adds, from Apple's Tim Cook to Warren Buffett.

"Confidence is serious business, and the single most important differentiator in the workplace," Low-Kramen wrote in her book, which published in February. "It will be the person with high confidence and lower abilities who will get the job over the person with low confidence and higher abilities."

Building the trait takes time, she adds, but it's worth the "power feeling" you get afterwards.

Here are three actionable ways to build your confidence, based on Low-Kramen's book.

For many people, saying "I'm sorry" after certain situations, even those that don't require an apology, is second nature. But apologizing unnecessarily can backfire, lowering your self-esteem and making others think less of you. 

 This is especially true for women, Low-Kramen wrote.

"Women apologize far too often, and when we do, it indicates lower self-confidence," she writes. "Replace 'I'm sorry' with 'Thank you.' Rather than saying 'I'm sorry, we need to reschedule the appointment,' say 'Thank you for working with my schedule.'"

This approach comes off as more assertive, and makes your apologies more impactful when you use them in the right situations.

Successfully getting your message across can also boost your confidence, but it's hard to do that when you're rambling or talking too quietly.

Instead, "slow it down, lower the pitch of your voice and turn up the volume" to be taken more seriously, Low-Kramen wrote.

"To speak quickly and too softly at a high pitch sends a message of low confidence. It may communicate that you just want to get a conversation over with and that your message is not worth hearing."

Speaking publicly may be more difficult, as 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.

In these cases, leadership researcher Simon Sinek has a simple hack for easing your mind.

"What I've learned to do is to interlock my fingers and to hold my hands still," he told Adam Grant's "ReThinking" podcast in a recent episode. 

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.

Actually doing something you set out to do can have a huge positive impact on your self-esteem and confidence, Low-Kramen writes.

"The process of deciding to do something, such as to study for and gain a certification or a degree is a quantifiable achievement that no one can dispute or take away."

Real estate mogul Barbara Corcoran experienced this firsthand. In 1973, early in her entrepreneurship journey, she recognized that all her competitors looked the part. Corcoran then set a goal to buy a fancy coat when she'd made enough money from her real estate brokerage, allowing her to also uphold a similar appearance.

She didn't expect to reach her goal "during her first week in business." But with her first commission check in tow, Corcoran bought the most expensive coat in Bergdorf Goodman, a $320 wool coat with a black and white print.

The accomplishment significantly boosted her confidence, she said in a recent TikTok video.

"My new coat made me feel just like the big deal I hoped to become," she said. "I wore my coat for the next four years, and it was the best investment I ever made. In my coat, I worked like crazy to become as successful as I already looked."

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