Elon Musk said Thursday his tweet about having “funding secured” to take Tesla Inc. private was only intended to show transparency, and that despite the furor — and SEC investigation — it caused, he has no regrets about posting it.

In a wide-ranging interview with the New York Times published Thursday night, Musk chronicled the events leading to that tweet, as well as this year, which he acknowledged has been exceedingly difficult.

“ “This past year has been the most difficult and painful year of my career. It was excruciating.” ” — Elon Musk, Tesla CEO

The Tesla chief executive described a constant state of exhaustion as the company has worked to ramp up production on Model 3 sedans, and said it was taking a toll on him.

“It’s not been great, actually,” Musk told the Times. “I’ve had friends come by who are really concerned.”

The Times said Tesla’s board was concerned about Musk’s workload and health, especially his use of the sleep aid Ambien, and that efforts are underway to find a second-in-command who could take some of the strain off of him.

As for the now-notorious tweet, Musk said he was referring to a potential investment from Saudi Arabia’s sovereign wealth fund, although the fund has not actually committed to investing. He admitted to the Times that no one had seen or vetted it beforehand.

He told the Times he has no plans to stop tweeting, and has no regrets about that tweet in particular — “Why would I?” he said.

The Securities and Exchange Commission is investigating the matter, and Musk could face charges if he was found to have intentionally misled investors.

He also addressed why he said the stock price for going private would be $420 a share — a reference that some at first thought was a joke, referring to marijuana. Musk said he wanted to price the stock at a 20% premium from its price at the time — which would have been $419 a share. So he rounded up. “It seemed like better karma at $420 than at $419,” he told the Times. “But I was not on weed, to be clear.”

Musk said he has recently been working 120-hour weeks, and sometimes would not leave the factory for days on end — including his 47th birthday in June. But while “production hell” appears to have peaked, Musk said his struggles are not over.

“The worst is over from a Tesla operational standpoint,” he said. “But from a personal pain standpoint, the worst is yet to come.”