Some of the most successful people in business have had to overcome serious hurdles to define their futures.
Steve Jobs was humiliated and felt pessimistic about his future after he was fired from Apple, the company he co-founded. Hip-hop titan and judge of ABC's "Shark Tank" Daymond John, who had worked hard to escape poverty, hit a low point when he lost nearly all of the money he made and couldn't afford to heat his home.
Media mogul Oprah Winfrey battled the traumatizing mental effects of childhood abuse, and faced sexual harassment and racism as a young professional trying to break into TV.
All three, however, said that working through these hardships made them stronger.
"The greatest discovery of all time," Winfrey once said on her TV show, "is that a person can change his future by merely changing his attitude."
And sometimes, as Winfrey says, it's our own mindset that's blocking the path forward. According to behavioral economics professor and business strategist Keld Jensen, nearly every professional will face serious doubts about whether or not he or she can succeed and find happiness in their work life.
In his book, "Intelligence is Overrated," the behavioral economist identifies 100 of the most significant thoughts that hold people back from great careers, based on his own research and experience in corporate consulting.
He notes, however, that as compelling as these thoughts may seem, they aren't fact.
Here are seven of the most common thoughts that are holding you back, as well as how to push past them:
1. I don't have the credentials
"Sometimes lack of credentials is an obstacle," Jensen writes. "Mostly it is not."
By industry standards, Jensen may not have the 'necessary' qualifications to succeed. He does not hold a Ph.D.
And yet he is an adjunct professor at the highly-ranked Arizona State University Thunderbird School of Global Management. He guest lectures at several other institutions, and he runs his own business and corporate strategy firm.
Jensen isn't alone in coming into a great career through a side door. Consider Bill Gates, Jobs or Winfrey, all hugely successful college dropouts.
"If you lack 'proper' certification, but know you're actually well-qualified, stop at nothing to get yourself in the door," Jensen writes, adding, "Of course, if it's important to you, you can also invest the time and money to earn a degree."