Oprah Winfrey has four decades of success behind her, a net worth of around $2.5 billion, and even knows the secret to getting every meeting off to the perfect start. (She asks these three questions.)

So where does the confidence to not just take big risks, but to achieve at such a high level, come from?

According to Oprah, confidence comes not from strength, but from vulnerability. As Oprah says:

"Most people think vulnerability is weakness. I live in the space of vulnerability... and that is what has made me so successful. 

"I think vulnerability is... the cornerstone of confidence. Unless you can allow yourself to take the risk, to be open, to live as a whole-hearted person. Do that and you recognize that you're just like everybody else, and that gives you the confidence to be yourself. Which is all you really need in life: To be more of yourself."

Vulnerability is also important for leaders. The best leaders don't project unshakable confidence. The best leaders realize that admitting weakness doesn't creating more weakness. Strong cultures can only happen when team members feel safe enough to tell each other the truth -- which starts with leaders being willing to show they're fallible.

But there's another important aspect to vulnerability: Science says people will like you more.

The More "Perfect" You Seem, the Less Likable You May Be

Say you're highly skilled. Exceptionally talented. Perceived as incredibly successful.

As the authors of this study write:

"If we assume that superior intellectual ability is a positive attribute and if we assume that people with positive attributes are more attractive... we should like people of superior intellectual ability more than mediocre, average, or stupid people. Yet, obvious as this relationship may seem, it is not always the case.

"It has been shown that group members who are considered the most able are not necessarily the best liked.

"It has also been demonstrated that people who initiate the most ideas and are acknowledged as the best 'idea' men or women by other members of their group are usually not the best liked group members.

"A great deal of ability, in and of itself, might make the stimulus person seem 'too good,' unapproachable, distant, non-human."

Or in non-researcher speak: The person who always has the best ideas, who consistently outperforms her peers, who tackles -- and crushes -- extra work, and still somehow finds time to do triathlons in her "spare" time?

We respect the (stuff) out of her... but we don't necessarily like her.

Unless she occasionally goofs up. And is willing to laugh at herself when she does.

Then we like her more.

Why? The phenomenon is called the pratfall effect. Depending on the individual's perceived overall ability to perform well, attractiveness increases or decreases after that person makes a mistake.

A highly-competent person is seen as more likable after the mistake; a person with average or below average competence is seen as less likable. 

Which makes sense: If Joe is a below-average performer and one day spills coffee all over himself during a meeting, we see that as yet another sign of Joe's overall suckiness. And that makes us like him even less.

But if Mary is amazing... and one day she spills her coffee? As the researchers write:

"A near perfect or superior individual who shows that he is capable of an occasional blunder or pratfall may come to be regarded as more human and more approachable; consequently, he will be liked better because of this pratfall.

"On the other hand, if a mediocre or average person commits an identical blunder... it will suggest only that he is very mediocre and will lower his attractiveness."

Vulnerability Leads to Confidence

All of which is yet another reason to be extremely humble -- especially if you're extremely talented. Try to do perfect work, but don't act like you're perfect. Admit a mistake. Share a screw-up.

And most importantly, laugh at yourself; while you should never laugh at other people, you should always laugh at yourself.

When you make an occasional mistake and are willing to laugh at yourself, other people won't laugh at you. They'll laugh with you. 

And they'll like you better.

That means showing vulnerability will actually lead to you feeling more confident.

Which means you'll be more successful.

Can't beat that.