When Neeleman was 34, he sold his second startup, Morris Air, to Southwest Airlines (LUV, Fortune 500), where he soon became a candidate to succeed CEO Herb Kelleher -- until Kelleher fired him. From that setback, Neeleman learned another lesson: Always be your own boss.
Then, at age 39, Neeleman founded JetBlue (JBLU). He built the airline into America's eighth largest and ascended into the ranks of the most admired and innovative CEOs. But when an epic ice storm hit in 2007 and revealed his deficiencies as a manager -- he staged a haphazard response plan and failed to communicate to the board -- he was ousted. From that, Neeleman learned many more lessons, including the need to design his next company so that his board can't toss him out.