Elon Musk has said that the past year has been "the most difficult and painful" of his career.
The 47-year-old South African is the CEO of electric car manufacturer Tesla and space transport company Space X.
In an in-depth interview, Mr Musk told the New York Times that the year has been "excruciating", and that the "worst is yet to come" from a "personal pain" standpoint.
His comments came a week after a controversial tweet saying he was considering taking Tesla private.
Am considering taking Tesla private at $420. Funding secured.
— Elon Musk (@elonmusk) August 7, 2018
The tweet is reported to have prompted a federal investigation by US regulators, amid concerns over its impact on the publicly-traded company's shares.
It has also emerged that there was no 'funding secured', although Mr Musk is said to have had 'extensive talks' with representatives of a Saudi Arabian government fund.
In the interview, Mr Musk insisted he doesn't regret the tweet, and "definitely did not get calls from irate directors".
He also stated he was "not on weed" when he tweeted.
He suggestion that investors who bet against Tesla shares - so-called short sellers - "are desperately pushing a narrative that will possibly result in Tesla's destruction".
'Personal pain'
Mr Musk has courted controversy on a number of occasions recently, including when he infamously referred to a Thai cave rescuer as a “pedo guy" - a remark he later apologised for.
He has also been under increasing pressure as Tesla struggles to meet demand for its Model 3 mass-market car.
The billionaire claims to have been working up to 120 hours a week recently, telling the Times: “There were times when I didn’t leave the factory for three or four days - days when I didn’t go outside.
"This has really come at the expense of seeing my kids. And seeing friends.”
He added that while the worst is over at Tesla, that is not the case personally.
In the interview, Mr Musk indicated that he sometimes takes Ambien - a sedative - to help him sleep.
He also claims to have not taken more than a week off since contracting malaria in 2001.
