Sarah Stanley Fallaw, director of research for the Affluent Market Institute, studied more than 600 millionaires for her book, "The Next Millionaire Next Door: Enduring Strategies for Building Wealth."
She found that how millionaires occupy their minds and time can influence how much wealth they build.
"Successful individuals are keenly aware of how they spend their resources, including their emotional and cognitive resources," Stanley Fallaw wrote.
She found that millionaires spend their time differently from the average American in five areas: reading, exercising, perusing social media, sleeping, and working.
next slide will load in 15 secondsSkip AdSkip AdMillionaires spend roughly 5 1/2 hours a week reading for pleasure, compared to the average American's two hours.
Consider celebrity Melissa McCarthy, who begins her morning reading The Los Angeles Times, National Geographic, and The New York Times.
Even billionaires spend a lot of time reading. Bill Gates is an avid reader and has quite the book collection.
And investor Warren Buffett, who spends 80% of his days reading, has said he has a "disgusting pile" of books by his chair.
In 2015, Mark Zuckerberg vowed to read one book every other week "with an emphasis on learning about different cultures, beliefs, histories and technologies," he wrote in a Facebook post.
next slide will load in 15 secondsSkip AdSkip AdBusinessman and investor Mark Cuban often reads for three hours a day to learn more about the industries he's working in.
But reading isn't the only hobby among the rich. Millionaires also spend more time exercising — nearly six hours a week compared to the average American's weekly 2 1/2 hours, Stanley Fallaw found.
Apple CEO Tim Cook wakes up around 4:30 a.m. or 5 a.m. every day to get to the gym.
Vogue's editor-in-chief Anna Wintour also rises early to get her exercise in, waking up every morning at 5:45 a.m. to play tennis.
Billionaire Richard Branson also exercises before breakfast and is a fan of playing tennis. He stays active by kite-surfing, swimming, and cycling.
next slide will load in 15 secondsSkip AdSkip AdOprah Winfrey's workouts include "45 minutes of cardio six mornings a week, four to five strength-training sessions a week, incline crunches, and stretching," according to her trainer.
And actor Mark Wahlberg is an overachiever; he works out twice a day, from 3:40 a.m. to 5:15 a.m. and at 4 p.m.
Millionaires may have more time to exercise because they spend less time on social media. The average American spends 14 hours a week on social media compared to the average millionaires' 2 1/2 hours a week.
Model and Kode with Klossie founder Karlie Kloss takes a weekly digital detox. "I will totally shut off and not post Instagrams or answer my emails," she told the Mirror.
McCarthy also takes digital detoxes, putting her phone away and disconnecting from technology on weekends.
next slide will load in 15 secondsSkip AdSkip AdSome don't have social media at all. Jennifer Lawrence previously told BBC Radio 1 that social media baffles her. She said she "will never get Twitter."
George Clooney has vocally opposed Facebook and Twitter. "I'd rather have a rectal examination on live TV by a fellow with cold hands than have a Facebook page," he once said.
And Buffett doesn't even own a smartphone — he still uses a flip phone.
But millionaires make a few sacrifices to make the most of their time — they sleep nearly eight hours less a week than the average American.
Tesla CEO Elon Musk typically crashes around 1 a.m. and wakes up at 7 a.m., averaging six hours of sleep — less than the recommended seven to eight hours.
next slide will load in 15 secondsSkip AdSkip AdMeanwhile, PepsiCo chairwoman Indra Nooyi wakes up as early as 4 a.m. She told Fortune, "they say sleep is a gift that God gives you ... that's one gift I was never given."
Source: Fortune via Business Insider
Fashion designer Tom Ford attributes his success not to talent, but to his energy — he's awake 21 hours a day, only getting three hours of sleep a night.
But he's not the only one — Martha Stewart is so busy running her business that she reportedly gets less than four hours of sleep a night.
Likewise, life coach Tony Robbins typically gets about three to five hours of sleep.
That's probably because he's busy working 16-hour work days, sometimes to the point of exhaustion.
next slide will load in 15 secondsSkip AdSkip AdRobbins' work hustle exemplifies another trait common among millionaires. They often work more than the average American — a difference of six hours a week.
Former GE CEO Jeff Immelt has said he worked 100-hour weeks 24 years in a row.
And Musk is known for his tireless work ethic and puts in 80- to 100-hour work weeks.
While Facebook COO Sheryl Sandberg leaves work at 5:30 p.m. to have dinner with her kids, she gets back to work online after putting them to bed.
And former Yahoo CEO Marissa Meyer used to put in 130-hour weeks while working at Google, which she managed by sleeping under her desk.