Elon Musk has admitted Tesla was within weeks of going bust earlier this year as it attempted to increase its electric car production.
Tesla's chief executive said the company was "bleeding money like crazy" after he promised to produce 5,000 Model 3 vehicles a week by the end of June this year.
"Essentially, the company was bleeding money like crazy, and if we didn't solve these problems in a very short period of time, we would die," the 47-year-old entrepreneur told HBO.
"And it was extremely difficult to solve them."
At the time the billionaire revealed he was at the factory 24 hours a day, seven days a week, and only sleeping for two hours to ensure his self-imposed target was met.
"People should not work this hard. This is very painful," the South African-born tech industry leader said.
"It hurts my brain and my heart.
"It hurts. It is not recommended for anyone. I just did it because if I didn't do it… there was a good chance Tesla would die."
In the same interview Mr Musk said there was a 70% chance he will go to Mars – and expects that he would "move there".
Tesla eventually reached its 5,000 a week target for the cheaper mass market model in June, but at a cost of $739.5m (£565.2m) in cash.
Mr Musk was forced to step down as Tesla's chairman, but remains as chief executive, after he was accused by US regulators of writing "false and misleading" tweets about potentially taking the company private.
The US securities and exchange commission (SEC) fined him and his company $20m (£15m) each after he told his 22m Twitter followers in August that he might take Tesla private at $420 per share and that there was "funding secured".
But the SEC said Mr Musk had not discussed or confirmed key deal terms, including price, with any funding source.
Mr Musk's tweets caused Tesla's stock price to jump by more than 7% on 7 August and led to "significant market disruption", the regulator said.
In response, Mr Musk called the lawsuit "unjustified" and said he was "deeply saddened and disappointed".
More from Elon Musk
He then mocked the SEC by calling it the "Shortseller Enrichment Commission", saying it was doing "incredible work".
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