Elon Musk has two huge companies to run in addition to Tesla, so the billionaire says he generally spends each day "predominantly" focused on only one of them.
"My days are very long and complicated, as you might imagine," Musk said at The Wall Street Journal's CEO Council last week.
"There is a great deal of context switching," he said, which he described as "quite painful."
Musk said he has just one part-time assistant and handles most of his own scheduling because "it's impossible for someone else to know what the priorities are."
He said he works most of the time he is awake and typically goes to bed at 2 a.m.
In the coming weeks, Musk plans to step down from one of his three CEO jobs after hiring NBCUniversal advertising chief Linda Yaccarino to run Twitter, which he bought last year for $44 billion. When Yaccarino arrives, Musk will become Twitter's executive chairman and technology chief.
Musk said he has made plans for who he wants to eventually take over for him at Tesla, Twitter and SpaceX. Do not expect it to be his 3-year-old son X AE A-XII, who often attends company events, or any of Musk's other eight children, the oldest of whom is 19.
"I am definitely not of the school of automatically giving my kids some share of the companies, even if they have no interest or inclination or ability to manage the company," he said. "I think that is a mistake."
Musk said he is weighing plans for how his ownership stakes in his companies would be handled after his death but has not made a final decision. But he has told the companies' boards who he wants to succeed him.
"There are particular individuals identified that I have told the board, 'Look, if something happens to me unexpectedly, this is my recommendation for taking over,' " he said. "So in all cases, the board is aware of who my recommendation is. It's up to them. They may choose to go in a different direction."