How one of America's richest self-made women went from model to mogul

Supermodel Kathy Ireland still graces the covers of magazines, but lately she's more likely to be on Forbes than Cosmo.

In fact, her most recent cover shoot was the Forbes June edition, which featured her as one of the richest self-made women in the U.S., with an estimated net worth of $360 million.

The model turned mogul is the founder and CEO of lifestyle company Kathy Ireland Worldwide. It has annual merchandise sales of more than $2 billion from licensing the brand out to some 17,000 products.

But moving from modeling to business wasn't easy, and she learned some valuable career lessons along the way.

"My old job description as a model was 'shut up and pose,'" Ireland told CNBC.

When she did speak, she said critics judged her every word.

"Some critics said publicly that I had a voice that could kill small animals. It was not a real confidence builder," the 53-year-old said.

But that didn't stop her from pursuing her longtime passion of entrepreneurship.

When a marketer approached her about an opportunity to model socks, Ireland made a counteroffer. Instead of modeling socks, she would be a business partner in creating the sock line. Soon after the deal, she launched her company in 1993.

In response to the man who ridiculed the sound of her voice, Ireland said: "It forced me to decide if I was going to allow the cruelty of that man's remarks to forever silence me, or if despite the criticism, I would choose to speak out."

That instance wouldn't be the only time Ireland faced demeaning or sexist comments, but she learned how to handle it.

"We've got to look at criticism and discern: Is there something of value I can learn from this, or is it just garbage?" she said.

Ireland decided not to be silent, and continued building her company. After landing a deal with Irv Blumkin of Nebraska Furniture Mart, a Berkshire Hathaway business, Ireland met Warren Buffett. The business legend told her to expand her brand.

She took his advice. Her company now sells products ranging from home office furniture to vases and will soon expand to sell diamonds.

In addition to dealing with external judgement, Ireland said it's important to quiet your own inner critic.

"Don't allow someone to put you in a box, and don't put yourself in one either," said Ireland, who also works with nonprofits like the YWCA and The Elizabeth Taylor AIDS Foundation.

Ireland also had advice for anyone interested in starting a business or a side project.

"First, you really have to believe in what you're doing," she said. "Don't own a business if you're not passionate about it."

If you've got a passion and you're doing well, be bold and go for it, she said.

And most importantly, "don't let your circumstances or someone else's opinion define you or destroy you," said Ireland. "Don't put limits on yourself."