Mine, All Mine! Think you should have complete control over your company? Think again.

Los Angeles hairstylist Billy Lowe has a well-known clientele, including Ellen DeGeneres and the cast of Desperate Housewives. When he's not working at his private Beverly Hills hair studio, he might be on his way to style hair on a talk show set or for a Hollywood charity event. His first hair-care product will hit the market later this year.

As in control as he appears, Lowe, 35, knows he can't control everything that happens to his 2-year-old company. Hollywood can be a notoriously fickle and demanding place, and market timing is largely a matter of luck. A few cancellations can throw off a day's sales projections and leave Lowe pulling out his hair. "Sometimes it catches you off guard," he says. "It's amazing some of the things that are out of [a leader's] control."

Which begs the question: As an entrepreneur, how much control do you really have over your company's performance? Unfortunately, less than you might think. Jeffrey Pfeffer, a professor of organizational behavior at Stanford University and co-author of Hard Facts, Dangerous Half-Truths and Total Nonsense: Profiting from Evidence-Based Management, says that two long-held assumptions of the business world- that CEOs are in control, and that they ought to be-are actually half-truths. In reality, CEOs face a host of unknowns where their impact is negligible to nonexistent, and these unknowns ultimately dictate organizational performance. "There's weather, currency fluctuations, competitors' moves and all kinds of stuff that [leaders] have no real [control] over," he says.