Overall, there are three things you need to do to find success and satisfaction early in life. That's according to Scott Galloway, a successful serial entrepreneur and marketing guru who is a professor at New York University's Stern School of Business. First, be prepared to work hard, Galloway tells CNBC Make It when asked how young people can best set themselves up to be successful and happy "before the age of 30."

Balance is a myth

"If you have real aspirations about being at the top of your field and in the top income percentile, I don't know anyone who has done that without having pretty much devoted 10 to 20 years of their life doing pretty much nothing but working," says Galloway, who co-founded his first company in 1992, the 400-employee consulting firm Prophet, which Galloway left in 2003. Since then he has founded multiple companies, including New York City-based L2 Inc., a 150-employee business intelligence firm that research company Gartner acquired for an undisclosed amount in 2017. He's also served on the boards of companies such as Eddie Bauer, Urban Outfitters and The New York Times Company. "Recognize the myth of balance," he says. "You may know somebody that volunteers at the ASPCA, has a great relationship with their parents, makes a ton of money and has a food blog. Assume you are not that person." "If you strive and expect to be in the top 10 percent of income earners, much less the top one percent, acknowledge that you're pretty much going to have time to work and to work out — and that's about it," Galloway says. The professor joked that such a formula can seem "depressing," but he's also noted that focusing almost exclusively on work at an early age can pay off dividends later in life. A lack of work-life balance in your 20s can mean a lot more balance and financial comfort later in life. There are also other more tangible factors that can lead to success and happiness, Galloway, 53, tells CNBC Make It.

"Get to a city"

One of the biggest is whether or not you move to (or near) a major city early in life. "Get to a city. Two-thirds of all economic growth are going to happen in cities," Galloway tells CNBC Make It. Galloway himself has split much of his career between cities — New York City and San Francisco. In addition to the obvious opportunity to earn more money by working in a major city (where the highest-paying jobs are typically located), Galloway says the other important reason to opt for urban life is that increased competition will force you to up your own game. "When you're in a city, you're playing tennis with someone better than you," he says. "If you've ever played tennis, and you're playing with someone better than you, your game gets better. You want to play tennis with the best, and the best 'players' — professionally, creatively — are in cities. "Get to a place where your 'A' game has to be an 'A-plus' game."

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