This is the second part of a three-part excerpt. It is an edited version of Chapter 3 of Maddy Dychtwald's book, Influence: How Women's Soaring Economic Power Will Transform Our World for the Better. (Voice, Hyperion) 

As CEO of legendary ad agency N.W. Ayer in New York, Mary Lou Quinlan had it all. "A huge office, a fantastic view, my own bathroom, hundreds of people reporting to me, galas left and right. I succeeded on anybody's ranking of success in advertising," she told me. She's a cheerful redhead with a warm laugh and boundless energy. Maybe you've seen her as a judge on the reality show American Inventor or as a regular contributor on the CBS program The Early Show, or perhaps you've read her books on marketing and the workplace, including Just Ask a Woman and Time Off for Good Behavior.

But even this amazingly successful woman felt the traditional corporate world wasn't working for her somehow. She didn't have enough time with her husband and she spent more time at her office than in her Manhattan apartment. "Between your own fear of failure and the way your boundaries get narrower," she says, "you can narrow yourself into this version of you that has nothing to do with who you really are."

Quinlan had achieved so much, but she hadn't created a life that let her truly be herself and shape her world in her own, unique way. In the three stages of financial awareness model [survival, independence, influence], I'd say she had reached independence but hadn't reached economic influence -- the ability to use her financial resources to make her mark on the world.

In 1998, she stepped away from the pinnacle of corporate success to start her own company, called Just Ask a Woman, a five-person firm focused on marketing to women. Since then, she has written books, magazine articles and columns, and has appeared often on television. Today, still running Just Ask a Woman, she says, "I don't have to be somebody else's version of me."

Quinlan was able to reach the stage of economic influence only because she'd moved through the earlier stages. She rose through the ranks of advertising on her own merits and used her growing financial confidence to save and invest until she had the financial freedom to break out on her own. She also approached the move cautiously, testing the waters, taking a sabbatical from her job to write and think about her next steps, then moving ahead. Ultimately, her well-established financial security and confidence gave her the freedom to launch her business.

"My resources and planning put me in a place where money did not have to be the No. 1 driver," she says. "I see a lot of women who say they feel stuck and want to follow a dream, but they're not doing what they need to do to get into that position -- putting money aside, putting their toes in the water; the dream is more likely if you don't just leap off the bridge hoping to get it. Women are great at starting their own businesses, but they need to go about it with a straight business head on their shoulders, understanding what the risks are and what they can tolerate."

Quinlan waited until she was in her mid-40s to make the leap, but many younger women aren't waiting that long. Aliza Freud was 35, a marketing executive at American Express, when she decided to start SheSpeaks, a social network marketing firm. "In my last job at American Express, my responsibilities were global and there was a lot of travel. It was a dream job in many ways, but it was not a dream when I was sitting jet-lagged in Japan with my husband and two children at home," she says.

Most corporate jobs today are still set up on the assumption that somebody else, like a wife, is at home taking care of the kids. Freud also felt restricted by the narrow requirements of the corporate world: They didn't fit her real self.

"Senior female executives often have this feeling that somebody is going to tap them on the shoulder and say, 'We just figured out you stink and you're not talented,' " she says. "They call it the 'impostor's theory.' I felt like that was happening to me and my female colleagues at all levels." The impostor's theory, first identified by two women psychologists in 1978, argues that many high-achieving women attribute their success not to their own smarts, experience and positive personal qualities, but to dumb luck, good timing and other factors.

As these women rack up more and more achievements and promotions, their fear of being "found out" intensifies. One possible explanation for this fear of being caught is that traditional (male) definitions of success and the trappings that come with them just don't feel quite right for women. That was certainly the case for Freud and Quinlan.

Another factor: To a certain extent and at certain companies, women are impostors, trying hard to play by men's rules in an environment created by and for men. As long as she felt like an impostor, Aliza's professional and financial success wasn't enough to let her project her authentic self into the world, to make an impact in her own way.

Certainly, not all women feel this way, and many have done stunningly well in corporate positions. Being a woman at Ogilvy & Mather in the 1970s, for instance, "was fabulous," says Shelly Lazarus, who rose through the ranks to become chairman of the company. "If you can't be brilliant, be memorable. If there were 15 people in the room, I tended to be remembered because I was the only woman there. There would come the inevitable moment when everyone turned to me and said, 'Well, Shelly, what do women think?' "

She says she always felt the freedom to manage in her style, to wear what she wanted and to be herself. "Part of that was because David Ogilvy had an amazing instinct for putting people in positions where they would be successful. It was a true meritocracy." It certainly helped that her husband, a pediatrician, had more flexibility than she did, and that their combined earnings gave them the financial ability to hire a nanny and outsource work that would once have been done by a stay-at-home wife -- giving Shelly the freedom to work "like a man."

Still, for every Shelly, there are dozens of Mary Lous and Alizas, leaving to launch their own businesses. And they're not just influencing their own careers: They're changing our economy for the better. Consider: Nearly half (47 percent) of all nongovernment employees work for small companies, and 60 percent to 80 percent of new jobs in the past decade were created by small firms. In 2008, at a time when big companies were filing for bankruptcy, closing their doors and laying off thousands of people, small businesses were adding jobs. Example: In July 2008, medium and large companies laid off 41,000 people. But small companies -- those with 50 workers or less -- were actually hiring. Not just a few employees, either. Small companies added 50,000 new jobs that June -- enough to hire all those fired by big companies that month, and then some. The trend was strong enough to prompt Nell Merlino, the founder of the Make Mine a Million initiative, to write in a blog on the Huffington Post: "Women will lead the country out of this recession."

Next: The Midadventures of Venture Capital