On Quora.com, a reader wanted to know what goes into the making of a great entrepreneur like Bill Gates, Steve Jobs, Elon Musk, or Richard Branson.

Justine Musk shed light on what it takes. As a former wife of one of the “extreme entrepreneurs” mentioned, she should know.

“Be obsessed,” she wrote three times. “If you’re not obsessed, then stop what you’re doing and find whatever does obsess you.” Then follow your obsessions until a a big meaty challenging problem begins to take shape. It should be one that affects as many people as possible, a problem you feel hellbent to solve or are willing to die trying.

Justine Musk’s advice seems right for all of us, not just those hoping to break into the top echelons of extreme entrepreneurs. “Pursue something because it fascinates you, because the pursuit itself engages and compels you,” she writes. And if you want to be one of those extreme people, “combine brilliance and talent with an *insane* work ethic.”