The best money advice no one ever wants to hear, according to a financial expert and bestselling author

Courtesy of Ramit Sethi

The second edition of Ramit Sethi's bestselling book, "I Will Teach You To Be Rich" is available May 14.

• Ramit Sethi is the author of the New York Times bestseller, "I Will Teach You To Be Rich."
• Sethi has been writing about money for 15 years and found his audiences are often resistant to one piece of advice: Earn more money.
• Most people don't think they have the time or know how to earn more money, whether it be asking for a raise, finding a higher paying job, or starting a side hustle or full-time business.
• Visit Business Insider's homepage for more stories.

Ramit Sethi has been writing about money for 15 years and found his audiences are often resistant to one piece of advice.

"Nobody wants to talk about earning more. There are lots of ways to earn more. That is a huge part of the pie that no one thinks about," Sethi told Business Insider. The second edition of Sethi's bestselling book "I Will Teach You To Be Rich" is available May 14.

"Earning more is tough for mass audiences to swallow because they've never really thought that they could earn more," he said. Many people have two misconceptions that keep them from earning more money, Sethi said.

"The first thing is, 'I don't have any time.' The second thing is, 'I don't have an idea,'" he said. "So that's a classic, but when they get it, it becomes really powerful because they've always thought of their money as a fixed pie and suddenly they're like, wait, I can actually expand the pie. And that's an amazing feeling."

In the new edition of his book, Sethi says there are at least three ways to earn more money - asking for a raise at your current job, searching for a higher paying job, or starting a business or picking up freelance work.

If you're asking for a raise at work, Sethi writes, start preparing three to six months before your annual or quarterly review. "Become a top performer by collaboratively setting expectations with your boss, then exceeding those expectations in every way possible," he wrote. Then, compile a "briefcase" of evidence to support your pitch for a raise. Finally, and most importantly, he writes, practice your negotiation. 

"Remember that getting a raise is not about you," Sethi writes. "It's about demonstrating your value to your employer. You can't tell them you need more money because your expenses are higher. Nobody cares. You can, however, show how your work has been contributing to the company's success and ask to be compensated fairly."

If your company doesn't offer growth potential, it may be time to look for a new job or pick up some work on the side, Sethi said.

"When you embrace the idea that you can earn more, one of the biggest surprises you'll discover is that you already possess skills others would pay for - and you've never even realized it," he said.

Refining or mastering a skill is our "strongest weapon" when it comes to building wealth, according to Cal Newport, an associate professor of computer science at Georgetown University and a bestselling author.

"It really is like a magic elixir for career satisfaction - be really, really good at something," Newport told Brandon, an early retiree, on his podcast, The Mad Fientist. "You could generate more money. You could generate much more autonomy and leverage over how you generate that money."

• Read more:
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• The first 3 things to do with your money when you get a raise or bonus
• 13 pieces of money advice you can't afford to ignore
• Here's exactly what to say to find out how much money other people make