It takes a lot of diligence and dedication to retire young when you are a millionaire who built your fortune on your own.

Some have done so since the age of 28, while others achieve financial independence at 50. In any case, retiring young is not something that everyone can handle.

As the FIRE (Financial Independence / Early Retirement) movement has grown, Business Insider has spoken with many young retirees over the years. They all tend to share certain habits that have helped them get to where they are now and maintain their financial independence.

These young retirees often start on the same path: assessing their financial status, cutting expenses, and diligently tracking their progress and spending. Once they retire, they try to spend less and less and often move to areas where the cost of living is lower, focusing more on experiences and living a life they love full of hobbies and travel.

These are top 5 habits of millionaires🔥

1. They keep an inventory of their finances

Leif Daahleen, the blogger behind Physician on FIRE , retired at the age of 43, said that everyone who retires young takes the same first step: taking inventory of their finances. He once told Business Insider's Tanza Loudenback that there are two things to do to plan for the future: calculate your net worth and figure out how much you spend annually.

"These two pieces of the puzzle will help you come up with a plan to achieve financial independence," he said. "It is difficult to get to any destination if you do not know the starting point."

2. They keep track of your net worth and your expenses.

Young retirees keep track of their finances, they keep track of their net worth to ensure their net worth on the road to financial independence.

Monitoring your net worth will “show you where the opportunities lie to improve your financial picture,” wrote JP Livingston , retired at the age of 28 with $ 2 million. "It's the fundamental habit that helps you build momentum from the rest of the things you do to grow your wealth."

Sam Dogen, retired at 34 and who runs the Financial Samurai blog , also emphasizes the importance of monitoring your net worth. "Please review your net worth like a hawk to know exactly where you stand and how much you have to go on," he wrote in a post published on Business Insider .

To stay in line with their target net worth, many young retirees also keep track of their expenses. "I have not met many young retirees who did not have an accurate understanding of their spending," wrote Steve Adcock, retired at the age of 35 .

3. They are austere

Joe and Ali Olson, school teachers who retired in their 30s, made strategically austere choices that allowed them to live on just $ 20,000 a year. “We keep driving the same cars… we eat a lot at home. Eating out was rare and it was a luxury, ” Joe told Business Insider in 2017 .

In two years, Angela Rozmyn, who wants to retire young, reduced her family's food spending from $ 2,000 to $ 800 a month, cutting back on fancy lunches and making fewer trips to the grocery store. She and her husband are saving almost 50% of their income and are planning to retire in their early thirties.

4. They don't spend too much on housing

As Tanja Hester wrote in her book Work Optional: Retire Early the Non-Penny-Pinching Way , reducing housing expenses can free you up thousands of pesos a month, something that may well be channeled into investments.

She and her husband lived in a "one-bedroom apartment in West Hollywood that they rented for years, even as our income increased and we knew we could move wherever we wanted," she wrote.

Meanwhile, The Olsons chose to live in a modest home, with little space, in an accessible area. This allowed them to buy properties that they could rent to generate income, even when they only had $ 80,000 in annual income between the two of them.

5. They focus on increasing their income

Planning to retire young is not just about spending less, but about making more money. "You can't always cut expenses, but you can always earn more money," Hester wrote .

Those who aspire to retire young increase their income by starting a business outside of their job, or seeking opportunities in a higher paying career, increasing their efforts in their current career, negotiating more money or becoming their own bosses, he wrote.

Grant Sabatier, retired at 30 with $ 1.25 million , has a similar mindset: Increasing your income is much more important than cutting your expenses, he says, because it can only be cut so far. "This gives you the opportunity to invest more money, more frequently, accelerating the accumulated amounts and the growth of your money," he wrote in the book Financial Freedom: A Proven Path to All the Money You Will Ever Need .