From Elon Musk by Ashlee Vance

One thing that Musk holds in the highest regard is resolve, and he respects people who continue on after being told no. Dozens of other journalists had asked him to help with a book before, but I'd been the only annoying asshole who continued on after Musk's initial rejection, and he seemed to like that.

"I think there are probably too many smart people pursuing Internet stuff, finance, and law," Musk said on the way. "That is part of the reason why we haven't seen as much innovation."

Musk tabulates the amount of flight time he endures per week to help him get a sense of just how out of hand things are getting. Asked how he survives this schedule, Musk said, "I had a tough childhood, so maybe that was helpful."

When Musk came into the meeting room where I'd been waiting. I noted how impressive it was for so many people to turn up on a Saturday. Musk saw the situation in a different light, complaining that fewer and fewer people had been working weekends of late. "We've grown fucking soft," Musk replied. "I was just going to send out an e-mail. We're fucking soft."

"That's my lesson for taking a vacation: vacations will kill you."

"I'm not sure why I'd want to talk about extremely sad events. It does no good for the future. If you've got other kids and obligations, then wallowing in sadness does no good for anyone around you. I'm not sure what should be done in such situations."

Because of the long hours that he worked and his eating habits, Musk's weight fluctuate wildly. Bags formed under his eyes, and his countenance started to resemble that of a shattered runner at the back end of an ultra-marathon. "He looked like death itself," Riley said. "I remember thinking this guy would have a heart attack and die. He seemed like a man on the brink." In the middle of the night, Musk would have nightmares and yell out. "He was in physical pain," Riley said.

"He has the ability to work harder and endure more stress than anyone I've ever met," Gracias said. "What he went through in 2008 would have broken anyone else. He didn't just survive. He kept working and stayed focused." That ability to stay focused in the midst of a crisis stands as one of Musk's main advantages over other executives and competitors. "Most people who are under that sort of pressure fray," Gracias said. "Their decisions go bad. Elon gets hyper rational. He's still able to make very clear, long-term decisions. The harder it gets, the better he gets. Anyone who saw what he went through firsthand came away with more respect for the guy. I've just never seen anything like his ability to take pain."

Once at SpaceX, the new employees found out very quickly if they were indeed up for the challenge. Many of them would quit within the first few months because of the ninety-plus-hour workweeks. Others quit because they could not handle just how direct Musk and the other executives were during meetings. "Elon doesn't know about you and he hasn't thought through whether or not something is going to hurt your feelings," Singh said. "He just knows what the fuck he wants done."

In regards to time, Musk may well set more aggressive delivery targets for very difficult-to-make products than any executive in history. ...... "He will pick the most aggressive time schedule imaginable assuming everything goes right, and then accelerate it by assuming that everyone can work harder."

The guiding principle at SpaceX is to embrace your work and get stuff done. People who await guidance or detailed instructions languish. The same goes for workers who crave feedback. And the absolute worst thing that someone can do is inform Musk that there's no way to get the cost on something like that actuator down to where he wants it or that there is simply not enough time to build a part by Musk's deadline. "Elon will say, 'Fine. You're off the project, and I am now the CEO of the project.  I will do your job and be CEO of two companies at the same time. I will deliver it.,'" Brogan said. "What's crazy is that Elon actually does it. Every time he's fired someone and taken their job, he's delivered on whatever the project was."