They say that if you want to become highly successful--especially if your definition of success involves entrepreneurship--you need to just quit your day job and do it.

Either you're committed or you're not, they say. Either you're a true leader and visionary--or else you're a truly pitiable wage slave.

The truth about that kind of advice? It's a false choice, and it's all wrong.

"Don't quit your day job," Daymond John, founder of FUBU and one of the most iconic Sharks on Shark Tank, told recently, recounting that for the first five years he ran his company, he was supporting himself by working full-time as a waiter at Red Lobster.

Or as he put it to Tim Ferriss a while back: "To the public, FUBU was a huge company. Little did they know that I was still serving them shrimp and biscuits!"

The reason? It's all just a simple mathematical equation.

(Here's Ferriss's answer to the same question--when should I quit my day job?--in his own interview with

Time, money, and people

There are only three true types of assets in the world: money, time, and people.

So, if you don't have money to spend on your business--most businesses take no outside capital and are 100 percent bootstrapped--and you're not making enough to support yourself from it, you have to spend time.

(Also, you can recruit other people. John had three of his friends working with him when he started FUBU, for example.)

Maybe, if your business makes sense and you figure out during the hours you can devote to it how to make it work, you'll ultimately make enough to support yourself from it.

But until then, find your Red Lobster.

"Let's say I was making an average of $40,000 a year" as a waiter while starting FUBU, John told "That's $200,000 of salary. I would have had to sell $1 million more product for FUBU to bring home the $200,000. But I didn't have to do that. I just had to sacrifice time."

Work first, glamour and glory later

John's net worth is now about $250 million. He's invested millions in Shark Tank startups, and he's also told interviewers that he actually lost between $20 million and $30 million when he first became wealthy--before he learned to manage his money.

None of that would have been possible without the relatively meager salary he used to support himself in the early days of FUBU. Just as important, it was also a hedge that minimized risk and took the pressure off to make long-term decisions based on short-term considerations.

If FUBU had failed, he explained, at least he wouldn't have run up huge debts just to live, and run the risk of going bankrupt personally or ruining his credit rating. That lack of pressure allowed him to build FUBU at a pace that made sense--and to ultimately take advantage of marketing triumphs that built the brand's popularity in the early part of the century.

But that meant he had to get up each morning, literally sew his company's early product himself during the day--and then head out to work at the restaurant between about 4 p.m. and midnight.

"I'd start the routine all over again the next day," he told Ferriss. "I did this for about two years straight."