Do something you're a little unready to do.

    Moving from Wisconsin to California for college and then changing her focus to symbolic systems --"a major I couldn't really describe myself, let alone to my father"--Mayer proved to herself that she could do things before she felt ready. Her biggest test, she says, came during her summer in Switzerland while she was a student at Stanford.

    And her A-ha moment came while shopping for food, of all things. "The first day, I went to the grocery store and got in trouble because, it turns out, you buy produce in Europe completely differently [than in America]." Mayer simply wanted to buy grapes (a fruit she so loved as a kid that her family nicknamed her "The Grape Ape"), but she couldn't master the process of weighing the fruit and printing the price sticker.

    "This woman just started yelling at me in German," Mayer recalls. The moment may seem trivial, but "I remember going back to my apartment and just being like, 'What was I thinking? I don't speak the language, I can't even buy produce here."

    "When you do something you're not ready to do, that's when you push yourself and you grow," she says she now realizes. "It's when you sort of move through that moment of discomfort of, 'Wow, what have I gotten myself into this time?'"

    Fortune's Pattie Sellers closed the interview with Mayer by reminding the audience of wisdom that Ginni Rometty, IBM's (IBM) new CEO, shared at the Most Powerful Women Summit in October: "Growth and comfort do not co-exist." Mayer would surely agree.