During stressful periods at work and in his personal life, Elon Musk would stay awake at night and vomit. He says working so hard has 'taken its toll.'

• Walter Isaacson's biography "Elon Musk" reveals the billionaire's struggles with stress.
• Musk's partners have described him staying up all night and vomiting.
• "I've been burning the candle at both ends with a flamethrower for a very long time," he told Isaacson.

Elon Musk may be the world's richest person, but his success has been accompanied by stress-related bouts of vomiting and insomnia, per Walter Isaacson's biography of the billionaire.