This is the No. 1 thing that holds you back from success, says 'Deal or No Deal' host Howie Mandel

Elon Musk and Richard Branson are two of the richest and most successful men in the world. While trying to replicate the achievements of these moguls might seem like a tall order, there's one main thing that could be holding you back from reaching significant triumphs of your own, says Howie Mandel, host and executive producer of CNBC's "Deal or No Deal": not taking action.

"If you really think about it, the only difference between you and Elon Musk is he did it and he was interested in it," Mandel says. Likewise, the difference between "you and Richard Branson is he did it."

So, he says, "I always go by : Just do it."

Take the idea you're passionate about and start turning it into something real.

A lot of people "freak out" because they haven't created the perfect blueprint to achieve their goals or , says Mandel, but what you need even more than that is the willingness to move forward.

Our culture of planning too much is not conducive to success, Mandel says. Often, people overthink and get paralyzed in analysis instead of taking action. "You see in your mind what is successful and you plan the endgame," he says, but you can't always predict the result.

So instead, Mandel suggests, "be a little more myopic and put one foot in front of another … Put your right foot forward, put your left foot forward and, lo and behold, you're ten steps ahead.

"But you can't sit here and go, 'I want to be 10 steps ahead, here's how I'm going to get 10 steps ahead, I'm going to make notes on the reasons to be 10 steps ahead … the ways you can take steps, the kind of shoes I might wear ....' You're just not going to do it. Planning is not doing."

That sentiment is shared by self-made millionaire Tony Robbins. He writes in a blog post that while can be great tools to help you organize your priorities, they can also "make you feel like you're being productive without actually accomplishing anything."

He suggests that, "instead of taking time out of your day to create and worry over a to-do list, you should turn to a more effective system for time management" called the Rapid Planning Method. It helps you think about your ideas, wants and needs on a grand scale, so that you can focus on your motivation for accomplishing a task rather than mundane tasks themselves.

When you do that, he writes, "it will provide much more motivation than a to-do list ever could."

Then you can take action.

Whatever your goal is, don't be discouraged if you don't make immediate progress, or if the effort takes you out of your comfort zone.

Mandel, who did stand up for "$25 a couple times a week" in order to make ends meet after moving to Los Angeles, says people often think, "'You know, I'd like to do that but it's just too dangerous,'" or too difficult, or too complicated. The upshot is, they never try.

But "life is uncomfortable," he says, "and as soon as you feel really comfortable, you're not really moving ahead. Anything that's great, anything that's fun, anything that's good for you is uncomfortable."

And the way to accomplish great things is to start by taking that first step.

"Deal or No Deal" premieres on CNBC Dec. 5.

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Video by Mary Stevens