Tesla Inc. (TSLA) CEO Elon Musk has admitted that stress is taking a toll on his personal health, following an “excruciating” year that he said ranks as the most “difficult and painful” of his career.

The tech entrepreneur told The New York Times in an emotional interview published Thursday night that he has been working up to 120 hours per week and occasionally takes Ambien to get to sleep. During the interview, journalists said Musk alternated between laughter and tears as he opened up about his busy work routine and recent controversies. "The worst is yet to come," he said about his personal pain after describing how he spent the full 24 hours of his 47th birthday working and almost missed his brother's wedding two days later.

The Going-Private Tweet 

One of the key questions Musk faced during the interview was whether he regretted his controversial decision to tweet last week about having the funding in place to take Tesla private. The outburst led his company to be accused of fraudulently misleading investors in order to drive up its share price and punish the short-sellers circling the stock. So far, these damaging allegations have resulted in Tesla being subpoenaed by government regulators and hit with two class-action lawsuits from investors who contend that the tweets violated federal securities laws. Sources speaking with the newspaper said his actions also angered board members. (See also: SEC Subpoenas Tesla.)

During the interview, Musk maintained that his social media post was based on repeated and ongoing assurances that the official sovereign wealth fund of the Saudi Arabian government was interested in bankrolling a buyout. The entrepreneur said he fired off the tweet, which could prove to be the costliest in history and even land him and his colleagues in jail, on the way to the airport, but had no regrets. “Why would I?” he said, when journalists asked if he rued tweeting his intentions.

He also said the tweet was an attempt at transparency and that no one had reviewed it before he posted it. Musk clarified that he chose $420 as the share price he would take the company private at because he wanted to offer a 20% premium over where the stock was trading at the time. The figure was $419 and he rounded up.

“It seemed like better karma at $420 than at $419,” he said. “But I was not on weed, to be clear. Weed is not helpful for productivity. There’s a reason for the word ‘stoned.’ You just sit there like a stone on weed.”

Overworked?

Musk raised eyebrows in April when he vowed to take on a more active role in the manufacturing of Tesla’s Model 3 sedan, following a string of costly delays. During the interview, the company’s CEO and founder revealed that he sometimes does not leave the Tesla factory for three or four days straight and had not taken more than a week off work since he was sick with malaria in 2001. (See also: Tesla 'Well On Way' To 5 - 6K Model 3s A Week: ISI.)

The entrepreneur confirmed that he has no intention of relinquishing his role as chairman and CEO, but added that if there is someone out there who could do his job better, “they can have the reins right now.” The newspaper reported that there is currently a search underway to find a No. 2 executive.