Source: Wal-Mart

Most highly successful businessmen and women are oddly apathetic about money. It is, at most, nothing more than a quantitative measure of achievement.

And to some, it isn't even that. "Money has never meant much to me," Sam Walton, the found of Wal-Mart, wrote in his autobiography, "not even in the sense of keeping score."

The same quality can be found among many of history's greatest investors. Warren Buffett provides a case in point, driving a modest car and living in the same house he bought decades ago for less than $40,000.

Wealth to people like Walton and Buffett is a byproduct of seeking success, and not the other way around.

Is this a coincidence? Does it tell us nothing more than the fact that these two men, and countless others, just happen to be indifferent to money while at the same time having an overabundance of it?

Or is there something deeper to this? More specifically, could there be a causal relationship between the two? Does being apathetic toward money actually help one amass it?

The (obvious?) answer to this is "yes," but it's probably not for the reason you're thinking.

Over the past few decades, we've learned a lot about human behavior and how it impedes our ability to make wise investment decisions. Greed influences us to buy stocks when they're high. Fear then causes us to sell when stocks are low.

The net result is that most investors (including hedge funds, for that matter) underperform the S&P 500 (SNPINDEX:^GSPC) by a wide margin.

"I won't do that again," we tell ourselves. But then the next bull market begins, and what happens? "This time is different," we conclude. And it's the same story all over again.

"We do it because we make investing decisions based on how we feel rather than what we know," says Carl Richards in The Behavior Gap. "Falling stocks scare us; rising stocks attract us."

How can you break this cycle? Or, better yet, how can you reverse it so that, as Buffett puts it, you're fearful when others are greedy and greedy when others are fearful?

The answer lies in objectifying money; making it an abstraction; becoming, if you're able to, apathetic toward it. It's only by doing so that you can loosen emotion's grip on your financial decisions.

Of course, herein lies the problem. Not caring about money -- beyond a comfortable subsistence -- is so much easier said than done.

"When most people say they want to be a millionaire, what they really mean is 'I want to spend a million dollars,' which is literally the opposite of being a millionaire," says my colleague Morgan Housel.

The point being, if you want to be rich, you need to stop caring about the trappings of wealth.