13. Tony Fadell

Founder, Nest

"I’m always doubtful. Everything I do is always doubtful. When you’re trying to differentiate, there’s going to be this gut sense, is this right? If you’re not having doubt, then you’re not pushing it hard enough or you’re not looking at the details close enough. You need to be feeling that doubt every single day."

14. Anna Wintour

Editor in Chief, Vogue

"It’s always about timing. If it’s too soon, no one understands. If it’s too late, everyone’s forgotten.”

15. Nathan Myhrvold

CEO, Intellectual Ventures

"We live in a society where technology is a very important force in business, in our daily lives. And all technology starts as a spark in someone's brain. An idea of something that didn't exist before, that once they have invented it —brought it into existence — could change everything. And that activity is generally one that's not very well supported."