By Catherine Dunn
FORTUNE -- Sallie Krawcheck and Patty Stonesifer -- once among the most senior women in their corporate fields – know a thing or two about starting over.
Krawcheck, who famously lost her job as head of Bank of America's (BAC) wealth management division during fallout from the financial crisis, this spring bought 85 Broads -- a network for professional women with some 30,000 members.
Patty Stonesifer, previously the highest-ranking woman at Microsoft (MSFT), who then went on to run the multi-billion dollar Bill and Melinda Gates Foundation, also got a new job this year. She's now president and CEO of Martha's Table, a nonprofit in Washington, D.C. that provides food and support services to those in need.
Are they "downshifting" their careers? No way, according to Stonesifer. "It's a sideways move," she said Thursday at Fortune's Most Powerful Women Summit. "The risk of my failing is greater now than it was at Microsoft."
Both Krawcheck and Stonesifer have ambitious causes in mind. For Krawcheck, who shot up the Wall Street ranks at Citigroup (C) and BofA, it's women's advancement in corporate life -- which she sees as paramount to U.S. economic prosperity.
"Every single bit of research I see says that having women in higher roles does good things," Krawcheck said -- from producing strong returns and lower market volatility, to shrinking the wage gap between men and women.
And she believes 85 Broads can help with that. "The number one unwritten rule for success in business is networking -- for everyone," she said.
For Stonesifer, the pull of Martha's Table was helping families break out of poverty. At the Gates Foundation she got to "think big," she said. But during the same decade as her tenure there, childhood poverty rates in the U.S. soared. "I was done being a benevolent bureaucrat," Stonesifer said.
Once at Martha's Table, she even tried living on a food stamp budget -- about $4 a day. She lasted one week. For families who have to stretch their allotment for an entire month, buying power all but dwindles by the third week. "You don't even want to think about what happens when your dollars get down that low," she said.
As Stonesifer tackles this next set of challenges, she told the audience she's always had a keen sense of the two things that drive her. One is a desire for "increasing knowledge," which is what she found so fulfilling at Microsoft. The other is social justice, where she now is focused.
To navigate the "career jungle gym" well, Stonesifer advised, is to "recognize that you're seeking passion in a different way."
Which also means recognizing when to walk away. Stonesifer retired from Microsoft at age 40. "Even the best jobs in the world have a sell-by date," she said.
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