https://phys.org/news/2018-08-elon-musk-hours-isnt-option.html

He then added, in an apparent reference to his long hours at work: "You think this is an option. It is not."

Musk was responding to an open letter from Huffington on Friday in which she called on him to change the way he works so he can ensure he's taking more time to "refuel and recharge."