Studies estimate that 70 percent of the population experiences impostor syndrome at one time or another. And for some people, it can be debilitating.

Impostor syndrome is the term used to describe high-achieving individuals who experience a persistent fear of being exposed as a "fraud." Despite their impressive accomplishments, their self-limiting beliefs prevent them from feeling successful.

Consequently, they experience negative thoughts and engage in unproductive behavior that keeps them from reaching their greatest potential.

Here are seven things people with impostor syndrome do:

1. They convince themselves they're frauds.

The more success they have, they more they worry about how much effort they're going to have to put in to keep up the "charade" that they are competent. Whether they're scientists or actors, they convince themselves they're not as good as other people.

2. They sabotage themselves.

Individuals with impostor syndrome are terrified of failure. At the same time, however, they're frightened by success. Although they want to prove themselves, they don't feel worthy of too much achievement.

Studies show this constant internal struggle leads to self-sabotage. They often ruin their chances for achievement by not breaking out of the cycle of self-doubt.

3. They think other people overestimate them.

Compliments, promotions, and awards don't help people with impostor syndrome feel better. Instead, they assume other people overestimate them. Meanwhile, they underestimate themselves.

They think things like, "My supervisor has no idea I'm not qualified for this project" or "My boss doesn't know I just got lucky that things worked out that time." Research shows this leads to increased worry that they won't be able to meet other people's expectations.

4. They work really hard.

In an effort to relieve some of their feelings of being inadequate, individuals with impostor syndrome work hard. They establish high standards for themselves and do their best to reach their goals.

But despite their best efforts--and the validation they receive--they feel that they fall short. And they continue to view themselves as incompetent.

5. They remain dissatisfied with their jobs.

It's rare for an individual with impostor syndrome to ask for a raise. They aren't able to recognize their contributions are worthwhile enough to ask for more money. Consequently, many of them never advance in the workplace.

Since they remain stagnant in their careers, individuals with impostor syndrome tend to be dissatisfied with their jobs. Yet studies show they aren't likely to seek new opportunities with other employers. They believe they can't do any better and worry that they can't succeed anywhere else.

6. They decline opportunities outside their role.

When you ask individuals with impostor syndrome to join a new committee or volunteer for tasks outside their comfort zones, they're likely to decline. Since they put all their effort into performing well at their main duties, they avoid new tasks​, studies show. They fear extra duties will distract them from and derail their efforts.

7. They refuse to celebrate their successes.

Although achievement leads most people to feel good about themselves, success deepens self-doubt in individuals with impostor syndrome. Each time they accomplish something new, their fear of being "found out" increases, studies show.

Individuals with imposter syndrome are never able to fully internalize their success. They worry they can't replicate their results. Instead, they attribute their good fortune to blind luck.

How to Get Help for Impostor Syndrome

If you experience impostor syndrome, you aren't doomed to stay caught in a self-perpetuating negative cycle forever. There are steps you can take to build your mental muscle and feel more worthy of your success.

Getting a mentor--and mentoring someone else--can be a good place to start. It can also be helpful to teach a course or start a blog. Sharing your knowledge with others will remind you of the wisdom and skills you've gained.

If your feelings of incompetence are seriously holding you back, seek professional help. A psychotherapist can help you begin to see yourself in the same positive light in which others see you.