Abigail Johnson, CEO of Fidelity Investments

Abigail Johnson is the CEO of mutual fund giant Fidelity Investments, which she's served since 2014 when she took over for her father. She's been chairman since 2016 at the company that her grandfather, Edward Johnson II, founded in 1946. According to Forbes, Johnson owns an estimated 24.5 percent stake of the firm, which has reportedly about $2.9 trillion in managed assets.

Her best advice: "I've passed along the same advice that I was given when I was a kid: Be cautious with leverage," she told Business Insider. "What I mean by leverage is buying assets with borrowed money. It's dangerous and can be financially toxic when people use too much credit card or home-equity debt to pay for current consumption."