People were recently asked in the CNBC and Acorns Invest In You Savings Survey how they would spend an unexpected $5,000 bonus.

Good intentions abound: More than a third of respondents said they’d pay off debt. Many others claimed they’d save for short-term expenses (22 percent) or invest for long-term goals (15 percent).

A measly 2 percent said they’d buy something they couldn’t otherwise afford.

Admirable. But unlikely.

The average American holds on to just 7.5 percent of their disposable income. Forty percent of people in the U.S. don’t have $400 set aside for an emergency, according to the Federal Reserve.

You wantto do the financially responsible things, so why is it so hard to actually do them?

“Spending is much easier than saving for most people,” said Stephen Brobeck, a senior fellow at the Consumer Federation of America.

Companies, of course, set out to separate us from our cash.

The average American holds on to just 7.5 percent of their disposable income.

“We’re bombarded by ads for products and shop in stores designed to encourage spending,” he said. At the same time, he added, “those without substantial assets receive much less encouragement from the marketplace to save regularly.”

Add to capitalism another force against our bank balances — evolution, said Teresa Ghilarducci, an economics professor at the New School for Social Research.

“Saving is not what neuropsychologists call a ‘selective trait,’” Ghilarducci said. “It’s not a trait that helps propagate the species.”

While interpersonal skills and trust are qualities that lead us to reproduction, she said, “a young person saving for retirement is a bit weird. ”

The blame shouldn’t be put on consumers for not managing their money well enough, she said, but on the student lenders, banks and auto dealers that offer them more debt than they can realistically handle.

When it comes to saving for retirement, Ghilarducci believes there should be a mandatory system in place that’s not based on “unrealistic discipline.”

Our own life experiences can also make us bad with money, said Edward Horwitz, director of financial psychology programs at the Heider College of Business at Creighton University.

People carry different “money scripts,” or financial beliefs that are shaped by our childhoods and communities, he said. These guide our behavior.

“We react emotionally around our financial decisions, and it occurs literally in nanoseconds,” Horwitz said. “Then we employ our rational thinking to justify those decisions.”

The only way to mend “maladaptive financial beliefs” is to get to know ourselves better, Horwitz said.

“You need to go back and think about these things in the moment,” he said. "Yeah, I do have a tendency to behave in this way, and I understand that comes from what I heard growing up or am pressured by society to do."

“You have to be aware of where these beliefs are coming from and how they derail your best financial decision making,” Horwitz added. “Then you have to take corrective action.”

This article is part of the "Invest in You: Ready. Set. Grow." series from CNBC and Acorns. Disclosure: NBCUniversal and Comcast Ventures are investors in Acorns.

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