'What Not To Wear' star Stacy London just detailed the key to protecting your time as a female entrepreneur: Saying 'no'

Chris Polk for Mastercard

Stacy London is the author of New York Times Bestseller "The Truth About Style."

• According to reality TV star and stylist Stacy London, women entrepreneurs need to say 'no' more often.
• London spoke at Mastercard's first Small Business Summit last month in a keynote conversation with actress Sophia Bush.
• They talked about the reasons women can be afraid to say 'no' in their careers and businesses and how to establish boundaries that will make them more confident in saying 'no.'
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Speaking as a woman, there's something about denying a request or favor that can bring sweat to our brows - be it a boss's email, a friend's happy-hour invite, a date's advances, or a business pitch.

"No" is not a word a lot of women are acculturated into using, especially those raised in more traditional environments. One study found that women have more difficulty than men saying no in the workplace, but that it can be tied to the roles, positions, and the types of requests women get to begin with.

Saying no is more of a skill that we learn to embrace and hone out of necessity. And the more your career grows, the more you need to make and enforce boundaries.

Take it from Stacy London, the reality TV star and stylist of "What Not To Wear" fame, who spoke at Mastercard's first Small Business Summit and gave a dose of honesty in a keynote conversation with actress Sophia Bush.

"We do, I think as women, have a tendency to say yes all too often. The 'no's are much harder because we don't know what we're supposed to say no to," London said.

Psychology research shows that gender alone does not determine how people communicate. For example, studies have found women score higher than men in "agreeableness" on average, yet both men and women can have agreeable or disagreeable traits.

Regardless of gender, boundary-making is an essential life skill that isn't always taught early in life, so it has to be learned in adulthood.

Why women don't say 'no' often enough

London mentioned two reasons women often fear the word. The first is the stigma that if they say no, people will suddenly see them and treat them differently. "People are going to think we're a bitch if we say no," Lond said. "Well they might, tough s---."

The second reason is uncertainty or indecision. It's difficult to say no if you haven't established our priorities or goals. But if you know what's important to you, you can make your calendar serve those goals.

The word no plays a crucial role in how you spend your time, London said. "That is something that you need to think about when you are building your brand," she said.

How to teach yourself to say 'no'

Honing the craft of saying 'no' starts with knowing exactly what you're saying it to. Establishing your priorities will provide clear boundaries around what you take on and what you pass along. "Being clear on what your goals are and saying no when things don't serve you or your company is essential for you, because you only have so much energy," London said.

Bush needed to identify the overarching theme of her career - which she said is telling women's stories - in order to decide what opportunities deserved her time. Once she named what motivates her, it made it easier to "say no to anything that doesn't fall under that umbrella," Bush said.

When your company or career has a clear mission, anything outside of that mission will fall away. Bush encouraged entrepreneurs to "figure out what it is that serves us and then lets us serve the world, and say no to everything else."