This is the No. 1 habit self-made millionaires share—and it's also the most overlooked, says money expert

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There are a handful of things that separate the ultra rich from everyone else: research has shown they tend to exercise regularly, maintain a healthy diet, save 10% or more of their income, read books and manage their time wisely.

But the most important — and most overlooked — habit they share that helped them grow their wealth, in large part, is their commitment to forge valuable relationships with individuals they aspire to be: positive, success-minded folks.

You are who you associate yourself with

That's what I discovered through my "Rich Habits" study, in which I spent five years interviewing and researching the daily activities, habits and traits of 233 wealthy individuals (with at least $160,000 in annual gross income and $3.2 million in net assets) and 128 low-income individuals (with at least $35,000 in annual gross income and $5,000 in liquid assets).

It's human nature to associate ourselves with like-minded people with whom we feel the most comfortable.

The ultra wealthy and successful, however, are a lot more selective when it comes to who they allow into their inner circle. Nearly all of the self-made millionaires I interviewed said one of their top priorities was cultivating "rich relationships" and avoiding the "toxic" ones.

'Rich relationships' are about mindset, not money

It's important to note that a "rich relationship" is defined by mindset, rather than wealth.

In other words, individuals who contribute to rich relationships don't necessarily have big bank accounts (though they do know how to save money and don't spend recklessly), but they all have lofty goals and aspirations — and they spend much of their time trying to achieve them.

"I limit my exposure to toxic, negative people," one individual in the wealthy group of my study told me. "Some of them may bring you down and infect you with their negativity, which can undermine your ability to creatively find solutions to problems and overcome obstacles."

And it makes sense, doesn't it? Those with a positive attitude are better able to stay focused on seeking and finding solutions to their problems. Positivity can make you a problem-solver, whereas negativity can make you a problem-finder.

Based on my research, individuals who contribute to rich relationships have at least one or several of the following traits:

  • Positive mental outlook: They're the entire opposite of downers; they bring an upbeat and optimistic type of energy to the table.
  • Gratitude: They are appreciative and focus on what they have, not what others have.
  • Encouraging attitude: They inspire and motivate others to pursue their dreams.
  • Hard work ethics: They take action on their goals and never quit.
  • Health-oriented: They devote time to taking care of their physical and mental health. This might mean engaging in leisure time or exercising.
  • Humility: They see egotism as a deficiency.
  • Future-oriented: They invest in themselves and for the long-term, instead of seeking instant gratification.
  • Open to feedback: They accept feedback — from their friends, colleagues, family and mentors — and see it as a means to pivot what they're doing in order to achieve success.
  • Loyalty: They are trustworthy, responsible and reliable.
  • Authenticity: They don't pretend to be someone they aren't. This is because they like who they are.
  • Influence: They have some degree of influence, power or recognition in their field of work. They can open doors for others that otherwise would have been closed.
  • Curious: They seek to improve their knowledge and skills in topics they want to learn more about. This might mean going the library, taking an online class or actively seeking mentors. 

As for the people who often contribute to "toxic relationships," they usually have a very pessimistic view on everything and a "poor, poor me" attitude. They rarely take any sort of responsibility for the circumstances in life.

Nurturing 'rich relationships'

Those in the wealthy group essentially see their relationships as trees: in order for their roots to grow, they must be nurtured.

Even billionaires Bill Gates and Warren Buffett agree that by choosing the right group of friends, you can push yourself to achieve bigger professional goals. "You will move in the direction of the people that you associate with," Buffett once said.

Making sure the relationship thrives and continues to do so over time takes a lot of work and commitment. Here are the four most common things the self-made millionaires in my study did every day to deepen and maintain their rich relationships:

  • Make hello calls: This is about gathering information while at the same time truly getting to know the other person.
  • Make happy birthday calls: When you wish someone a happy birthday, it says to them that they're important to you.
  • Make life event calls: Life event calls (e.g., to people who just had a baby, got married, experienced a death in the family) are critical. Those you reach out to will never forget your kind and thoughtful gesture.
  • Network: Participating in or running business organizations, nonprofits or trade associations is critical to success. Plus, it's how you meet influential people who can add to your rich relationships.

We are only as successful as the people we spend the most time with. If you want to create and grow your wealth, you have to evaluate each of your relationships and determine whether it's rich or toxic.

Tom Corley is an accountant, financial planner and author of "Rich Kids: How to Raise Our Children to Be Happy and Successful in Life" and "Rich Habits: The Daily Success Habits of Wealthy Individuals."

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