This story is part of the Behind the Desk series where CNBC Make It gets personal with successful business executives to find out everything from how they got to where they are to what makes them get out of bed in the morning to their daily routines.

Jamie Kern Lima's story sounds like a dream.

After working as a waitress at Denny's, as a contestant on "Big Brother," and as a local news reporter in Washington and Oregon, the former beauty pageant winner, Kern Lima launched her own business at 31. Within eight years, Kern Lima sold that company, IT Cosmetics, to L'Oreal for $1.2 billion in cash. It made Kern Lima a very rich woman — according to Forbes, she pocketed roughly $410 million from the deal, and is worth roughly $460 million today. Kern Lima also stayed on with IT for three years, making her the first female CEO at L'Oreal.

But behind the scenes, Kern Lima had to overcome years of rejection while pitching her products, as well as self-doubt. She worked 100-hour weeks and at one point was down to her last $1,000. She says she drove herself to the point of exhaustion.

"I lived completely burnt out for almost a decade," Kern Lima tells CNBC Make It.

Today, however, Kern Lima, 43, has figured out a way to be ambitious while taking better care of herself. In 2019, she stepped down as IT Cosmetics CEO and recently published a memoir, "Believe It: How to Go from Underestimated to Unstoppable."

Here, Kern Lima talks to CNBC Make It about overcoming years of rejection, her "toolbox" for success and learning to take time for herself.

On rejection: 'I would read inspiring quotes'

There were nights [early on] where I was crying myself to sleep because of another big rejection [pitching the products].

I would literally pull up the notes app on my phone and I would read inspiring quotes or stories. It would remind of things like, "Oh, where I come from doesn't have to determine where I'm going," or "champions aren't made when the game is easy."

Everything in the world that is incredible was created by someone like you and me, and all those things just remind me of who I am, what I am made up and where I'm going.

I think we all need a toolbox [for] those things. Otherwise, in so many ways, we're alone and trying to navigate everything.

On her biggest mistake: 'I lived completely burnt out'

One of the things that I did wrong was I lived completely burnt out for almost a decade. I think this is so tempting for people, especially entrepreneurs and people going after a goal or a dream they care so much about.

When success started happening, it was almost as if I couldn't believe it for a while. I constantly felt like I needed to strike while the iron is hot. I drove myself so hard to the point of complete burnout. I did 100-hour weeks for almost 10 years. And I don't think you have to do that at all to have the outcome that we had.

I had to have a real come-to-Jesus moment with myself, where I'm like, "Ok, I'm completely addicted to work, completely addicted to busyness." Busyness and work addiction are like any other forms of addiction, when it numbs out all the good and bad emotions in life and separates us from ourselves.

On not taking the business public: It was a parallel journey

I just realized that if we go public, like I want the sexiness of ringing the [New York Stock Exchange opening] bell and all those things, but at the end of the day, I'll still be working 100 hour weeks. I didn't trust myself not to do that.

So I made the decision that if we actually partner with someone, at L'Oreal, then our mission can still grow and get out there probably way faster than we could do on our own.

But then also I needed to start making changes in my life, like I went almost a decade without seeing my friends or family very often.

My husband believes that us choosing to [sell to L'Oreal rather than go public] is why we were able to start making changes in our own life.

On her daily routine: 'I meditate and pray'

I walk for an hour every morning. I meditate and pray.

I have so much more energy in my life right now. The truth is for this book launch, I'm working 20-hour days but I feel so much better.

The biggest achievement for people to figure out how to still go after their passion and their dream and still be a good steward or a good owner of a body and of healthy relationships. I wasn't able to do those things for a long time.

And I usually text at least a few people every day to express gratitude. What we focus on magnifies and grows bigger. It helps me appreciate life and feel the day more.

This interview has been edited for length and clarity.

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