A financial psychologist claims that it is possible to become a millionaire while working at McDonald's.

• Financial psychology plays a big role in people's financial success.
• According to behavioral finance expert Brad Klontz, adopting a "rich" mindset can help anyone become a millionaire.

After the tech bubble burst in the early 2000s, Brad Klontz became interested in financial psychology.

After witnessing a friend make over $100,000 in stock trading within a year, Klontz decided to give it a try. However, he experienced immense embarrassment when the market crashed and his investments disappeared.

He aimed to uncover the reasons behind his risky behavior and explore ways to modify his actions in the future.

Klontz is a certified financial planner and an expert in behavioral finance. He is a member of the CNBC Financial Advisor Council and the CNBC Global Financial Wellness Advisory Board.

Perhaps, psychology is the biggest obstacle to people's financial prosperity, in his view.

"Start Thinking Rich: 21 Harsh Truths to Take You from Broke to Financial Freedom," co-authored by Klontz and Adrian Brambila, aims to break down mental barriers to financial freedom.

CNBC interviewed Klontz about the "harsh truths" that people earning a McDonald's salary can still become millionaires by changing their mindset.

The conversation has been edited and condensed for clarity.

'It's all about the psychology'

Greg Iacurci: Why is psychology important when it comes to personal finance?

Financial literacy is important, but I believe it's mostly about psychology when it comes to the basics of personal finance.

The two biggest problems Americans face are overspending and not saving and investing for the future. This is a widely known fact, and I have yet to meet an adult who is not aware of it. Therefore, the issue is not a lack of knowledge about retirement accounts like Roth IRA and traditional IRA.

I believe it's more about psychology than a lack of knowledge.

How does people's psychology often hinder them?

The primary obstacle: money beliefs. Many individuals are unaware of their attitudes towards money. There is a comprehensive procedure for identifying these beliefs. One aspect of this process involves examining your financial flashpoints, which are early experiences with money or those of your parents or grandparents. People often replicate this pattern in their families or take the opposite approach.

The difference between 'broke' and 'poor'

Can you clarify the distinction between being broke and being poor, as you mentioned it early in the book?

BK: We're talking about a poor mindset.

Having no money is what it means to be broke. I've been broke, as have my co-author and our families. However, being broke is not the same as having a poor mindset, which can keep you broke forever.

People who make six figures or more and have a poor mindset often lose their money, regardless of their financial success. This is because having a poor mindset can lead to poor financial decisions and ultimately result in the loss of money.

Can individuals overcome poverty regardless of their socioeconomic background by adopting a positive mindset?

BK: Yes.

GI: Is that one of your "harsh truths"?

We present the information in various ways depending on the [chapter] headings. For instance, "Being born poor is not your fault, but dying poor is." This statement presents a stark reality to readers.

Adopt a 'rich' vs. 'poor' mindset

GI: What is a rich mindset?

BK: It's an approach to life and an approach to money.

A future-oriented mindset is crucial for success, as it involves having a clear vision of the future and planning accordingly. On the other hand, a poor mindset that is focused solely on the present can hinder progress and prevent individuals from achieving their goals. Without a clear vision of the future, individuals may not save, invest, or live below their means.

A rich mindset values owning time over owning possessions, while a poor mindset is inclined to trade time for material possessions.

GI: What do you mean by that?

A mindset that prioritizes material possessions can lead to a lack of financial stability and savings.

Owning as much time as possible is a rich mindset. It's like thinking of retirement, where you don't need to work anymore to fund your life. They have a future orientation and think, "Every dollar I get, I'm taking some of that money and I'm going to put it over here so that I can own my time and eventually have that money fund my entire life."

One of the 'most destructive beliefs about money'

The notion that wealthy individuals are prodigious spenders could be one of the most detrimental beliefs about money that exist.

We compared two groups of people with different net worths: one group with about $11 million each and another with about $500,000 each. Despite having almost 18 times more money, the group with higher net worth only spent twice as much on their house, vacation, watch, and car.

The wealthiest people have money-vigilant money scripts, which is the belief that it's crucial to save.

Those who are the most flamboyant spenders have "money status beliefs." They come from lower income and net worth, and are more likely to come from poorer homes. Their focus is on displaying their wealth to the world, but this mindset keeps them broke.

I had it all, including the insults about my poor mindset.

How to work at McDonald's and be a millionaire

What is the most effective action people can take to protect themselves?

Your political party won't rescue you, your corporation disregards your well-being, and your outdated views on money are hindering your financial prosperity.

The outcomes in my life are a result of my actions, decisions, and knowledge. It can be challenging to accept this mindset.

It's important to recognize that no matter who the president is, they cannot guarantee financial freedom. They won't provide a check to make you financially free. Your company doesn't want you to be financially free as it would require them to replace you at a high cost. Even your teachers can't teach you financial freedom as they themselves are not financially free.

The bottom line is, you have to do this yourself.

What is the purpose of the rewritten sentence?

GI: And what is the answer?

BK: The answer is really, really simple.

Before doing anything else, you will allocate a portion of the $1 towards achieving financial freedom.

If you have the mindset to work at McDonald's your entire life, you can become a millionaire.

Save 30% of your income — or get a roommate

GI: What is the percentage people should be aiming for?

The percentage of savings and investments required to achieve wealth depends on individual preferences and goals. While some experts recommend saving and investing at least 10% of income, I believe a higher percentage, such as 30%, can help individuals reach their financial goals faster.

If you have a mindset that you can easily manage your finances before getting your first job, it becomes challenging when you've built your entire life around 100% of your paycheck. To overcome this, you need to make cuts.

"Get a roommate, get on the bus, get sober, get bald, and get a side hustle or shut up about being poor" is the title of a chapter on cutting expenses.

We often hear the excuse "I can't afford to invest," but we're calling bulls*** on it. Yes, you can.

We examined the typical monthly expenses of Americans, including rent, car costs, salon visits, and alcohol consumption. On average, Americans spend $2,000 on rent. If you share an apartment with a roommate, you can cut your rent in half, saving $1,000 per month. By investing the difference between the two amounts, you could have $1.3 million in 25 years. If you had three roommates, you could potentially earn $2 million. Just imagine the financial benefits of this simple change. This is based on average market returns.

If you take the bus, stop drinking alcohol, and shave your head, you could earn $2.8 million in 25 years.

GI: If you do all those things?

To achieve the same level of success as the richest people you know, you should avoid going to the salon, drinking alcohol, and riding the bus. Instead, you can watch YouTube or ask your friend to cut your hair.

I would say to you all: That sounds terrible.

To become a millionaire, you should invest 30% of every dollar you earn. However, if you take your investments and do something reckless, you may not achieve your goal.