5 things to give up to retire by 40, from real people who have done it

Retire by 40 by giving up these habits

As a handful of everyday people have shown us, retiring early is more than possible if you're willing to make a few sacrifices.

To give you an idea of just what it takes to retire before 40, CNBC Make It turned to those who have already done it.

Here are five things early retirees gave up to leave the workforce in their 20s and 30s.

Mindless spending

Several early retirees agree that the first step to achieving financial freedom is to track your spending. After all, "you have to know what you are spending before you can plan your retirement budget," say Justin and Kaisorn McCurry, who banked more than $1 million in a decade to retire in their 30s.

Plus, "knowing how you spend lets you determine whether you get value for your dollars, and where you might be able to focus efforts to reduce expenses further," the couple says.

Here's how this North Carolina couple could retire in their 30s

Lifestyle inflation

If you want to settle down early, it's time to stop living up to the ceiling of what your income allows. If your earnings increase, don't boost your spending; rather, put that extra money directly to savings.

It worked for the McCurry family: They made sure to "bank any raises we got," they tell CNBC Make It.

The same strategy can be used for any small windfall, like a bonus or birthday check. Instead of planning trips or grabbing gadgets, consider directing at least some of it towards lingering debt, a retirement savings account or an emergency fund.

How this couple saved over $1 million in retirement savings to retire by 43

Excess living space

One of easiest ways to save big and boost your retirement savings is to start with your most significant expenses, like housing.

"Focusing on big ticket items can get you to perhaps a 20 to 30 percent savings rate," says J.P. Livingston, who retired at age 28 with a $2.25 million nest egg. If possible, downsize, she tells CNBC Make It.

Think about it this way: "To buy a home with an extra bedroom or one with fancier finishings might cost you $50,000 or $100,000. Is that worth working three extra years to you?"

A New York City-based millennial who retired with $2.25 million says this is the key to saving

A willingness to wait and see

Money doesn't simply appear. If you want to build enough wealth to retire early, you have to have a clear goal and a specific plan.

Start by thinking about your future lifestyle and what it might cost, say the McCurrys. Do you plan on traveling a lot, or buying a vacation home? Do you want to give money to family members?

Next, project how your spending will change in retirement. "You will spend less in some categories, like commuting, and will probably spend more in other categories, like entertainment, recreation and travel," the couple says.

Finally, set your retirement budget, which will help you determine exactly how big your portfolio needs to be to last through your golden years. Once you have your "magic number," you can calculate how much you need to set aside each month to reach your goal.

This couple retired in their 30s and travels full-time in an Airstream trailer

Your comfort zone

Don't underestimate the power of escaping your comfort zone, says Steve Adcock, who retired in his 30s with his wife Courtney.

"It alters, in a healthy way, our outlook on life," he writes for CNBC Make It. "Getting out of your comfort zone is a mind-game and one that helps break an all-too-common addiction to spending."

And ultimately, "becoming more comfortable in uncomfortable situations helps to ease the mental component of quitting work early in life."

This is an update of a previously published story.

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