Amid one of his most important milestones, Elon Musk, CEO of Tesla Inc. (TSLA), SpaceX, the Boring Company and Neuralink, was candid on Twitter Inc. (TWTR) about his mental health. After seeming downbeat in a media briefing ahead of the automaker’s Model 3 release on Friday, in which Musk indicated that next few months could be “manufacturing hell” for the Silicon Valley electric car company, the tech legend surprised his 11 million Twitter followers. (See also: Tesla’s Model 3: Musk Warns of 'Manufacturing Hell'.)

Speaking candidly—which is characteristic of the billionaire—Musk responded to a fan who noted that Elon’s life on Instagram looked amazing. “I wonder if the ups and downs he had make for a more enjoyable life?” asked Musk’s Twitter follower.

Achieving Tesla's 2006 'Master Plan' Goals

“The reality is great highs, terrible lows and unrelenting stress. Don’t think people want to hear about the last two,” he responded. The tech executive was then asked, “Are you bipolar?” to which he responded, “Yeah,” in one tweet and, “Maybe not medically tho. Dunno. Bad feelings correlate to bad events, so maybe the real problem is getting carried away in what I sign up for.”

The tweet stream marks the first time Musk directly spoke to his personal mood swings and the psychological challenges of being a successful CEO of multiple companies. When asked if he could share more about his “lows and the stress and how he’s dealt with them,” Elon responded, “I’m sure there are better answers than what I do, which is just take the pain and make sure you really care about what you’re doing.”

Musk’s honest remarks on social media come as he achieves one of the main goals laid out in his original “Secret Tesla Motors Master Plan” in August 2006, in which he sought to offer a more affordable, yet still highly desirable, mass-market electric car. (See also: Zuckerberg and Musk Clash Over the Future of AI.)

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