A maniacal sense of urgency is our operating principle, he repeatedly declared. The sense of urgency was good for its own sake. It made his engineers engage in first-principles thinking. But as Mueller points out, it was also corrosive. If you set an aggressive schedule that people think they might be able to make, they will try to put out extra effort, he says. But if you give them a schedule thats physically impossible, engineers arent stupid. Youve demoralized them. Its Elons biggest weakness.

Elon Musk by Walter Isaacson