Lots of successful business people like to wax philosophical about the single most important trait that an entrepreneur must possess. For Tracy DiNunzio, founder and CEO of clothing buying and selling site Tradesy, that trait is adaptability. But coming from DiNunzio, the advice carries serious gravitas: DiNunzio was told as a child that she would never walk, due to a birth defect. On the contrary, she formed several successful businesses--and she learned to dance along the way.

DiNunzio recently shared her insights as part of UC Santa Barbara's Distinguished Lecture Series. Here are some key takeaways about the amazing power of adaptability. (Note: I am an investor in Tracy's company via Rincon Venture Partners.) 

"There's no such thing as the guy who's like, 'I started my business and it just took off--it was awesome.' When you hear people saying that, they are lying."

Instead, expect rejection, failure and deadly market conditions, she said, and always come back to that adaptability.

"It's grueling and difficult for every single entrepreneur, no matter what their circumstances. The ones who win are the ones who're adaptable."

When DiNunzio's artistic career in New York hit a plateau, she decided to make a major life change. Much to the surprise of her friends and family, she gave up the life of a celebrated, young artist to pursue an entirely different path--uprooting her life and moving to Mexico.  

"I tried to say, 'I can't dance. I can't even feel my feet.' I assumed that not being able to feel your feet would kind of eliminate you from being able to dance. As it turned out, not so much."

DiNunzio suffered from a lifetime of pain, due to a birth ailment which affected her back, legs and feet and prevented her from walking. That changed during her time in Mexico, when a Salsa instructor showed her that what she thought of as a limitation could be construed as an asset. "Because he was a really good partner, he was able to compensate for the things that I couldn't do. (He) even used the fact that like my feet were fused and I couldn't feel anything to do some crazy tricks that would've probably hurt someone else's feet. We toured different parts of Mexico doing dancing exhibitions, which was crazy, because I thought I wasn't even going to walk, let alone dance."

"You're probably making assumptions...about what you can and can't do. They might be true, I don't know. But they might not be true, so you have to test them."

At healthy start-ups, unbiased, verifiable, empirical data trumps assumptions, preconceptions and opinions every time. It was the opinion of medical experts that DiNunzio would never walk--and so she assumed she could never dance. It wasn't until she summoned the courage to test her assumption that she realized it was wrong. She took that lesson with her to business and applies it relentlessly--something I also suggest entrepreneurs do, by writing down and challenging each of the assumptions that are holding you back.

"Data wins," she says. "So whatever you're thinking is going stop you or the circumstance that's dictating the decision that you're making, just make sure you test it first because you might be able to dance, you don't know."