If you're the entrepreneurial type, Elon Musk is probably one of your heroes. And why not? Musk is one of the boldest minds of his generation, who is simultaneously trying to wean us off gas-powered cars, send us to Mars, directly link up computers and brains, and solve L.A.'s traffic problem (all bets are off on which of those goals is the hardest).

Oh, and of course there's his $15 billion net worth, which isn't too shabby either.

But being a mega-entrepreneur isn't all about working on fascinating problems and living large. The brutal truth is that playing at Musk's level comes at an incredibly high cost, one most of us mere mortals wouldn't be willing to pay.

And that's not just some random writer mouthing off. It's a truth that came from Musk himself this week. In a series of tweets, the Tesla and SpaceX boss leveled with a fan about the brutal realities of his life (hat tip to investor Fred Wilson):

"Starting and running companies brings stress that seemingly never stops. Managing that so that it doesn't eat you up and mess up your relationships is super hard," agrees Wilson, who, in his role as adviser, has seen many entrepreneurs struggle to cope.

Randi Zuckerberg, Mark Zuckerberg's sister, has observed the startup rocketship up close, and has said much the same thing about life as an entrepreneur. Work, sleep, family, fitness, or friends: Founders can pick only three, she insists.

The Zuckerbergs and Musks of this world aren't immune from brutal tradeoffs. We already know about Musk's insane workweeks, Mars-bar-for-breakfast health routine, and several divorces. In the back and forth following his original tweet, he also admits to being "bi-polar," though he suggests he means the term not in a clinical sense, but instead to convey the gut-wrenching highs and lows of entrepreneurship. Whether he's gotten a doctor's diagnosis or not, it's clear that, for Musk, huge success leads to huge stress.

Still, Musk isn't about to trade in his high-octane lifestyle for some quiet retirement in the country. He concludes the conversation by saying, "If you buy a ticket to hell, it isn't fair to blame hell ...," suggesting he's actively chosen his path with his eyes wide open.

Entrepreneurs who aspire to Musk-like greatness should be equally honest with themselves about what they're aspiring to. Musk's life is inspiring, it's interesting, and it's hugely meaningful, but it's definitely not happy. Not in any conventional, feel-good sense, at least. If you're aiming to emulate Musk, that's what you're signing up for too.