Many who have succeeded in their careers pass down the same mantra to aspiring professionals: Do what you love, and you’ll never work a day in your life. But Suzy Welch, author and NYU Stern School of Business professor, says the age-old advice to chase a dream job is deeply misguided.

“The very worst career advice my students get all the time, and I certainly got, was to do what you’re passionate about,” Welch said in a recent interview with the WSJ. “What dumb, dumb advice.”

It’s natural for workers to want to buy into their career fantasies—and there are a litany of success stories of people who have done it.

But the management professor rationalizes that there are too many stipulations at play for some aspirations to hold up in the real world. In some cases, people simply aren’t built for the careers they yearn to follow; without the right talent or temperament to make it in the industry, it’s hard to turn a passion into a full-time career.

“I hate it because you have to be good at it also. You have to be good at it, otherwise it should be a hobby,” Welch continued. “There’s also your emotional wiring. Some jobs require different kinds of personalities. Your personality is actually how the world experiences you. And the sooner you face into that, and know how the world experiences you, the better.”