Knowing you should do something is one thing, but actually doing it can sometimes be a challenge. For example, most adults understand that they should floss multiple times a day, but not everyone does because the impact of not doing so happens well down the road.

The same is true when it comes to saving for the future. It's about as fun as flossing and the negative impact of not doing so takes place far in the future. That, plus the fact that saving for tomorrow requires sacrifices today makes it easy for a surprising amount of working Americans to simply not save any money at all.

In fact, 20% of working Americans have failed to save a single dime for retirement, emergencies, and other financial goals, according to a report.

A green piggy bank sits on a calculator.

It's easy to not save, but that can lead to big problems. Image source: Getty Images.

What did the survey say?

While 20% aren't saving at all, the news is not all bad. Among those who are putting at least some portion of their paycheck away, 27% are saving more than 10% while 16% save more than 15% of each paycheck.

"With a steady, significant share of the working population saving nothing or relatively little, it's virtually guaranteed that they'll be unable to afford a modest emergency expense or finance retirement. That amounts to a financial fail," said senior economic analyst Mark Hamrick in a press release.

Why aren't Americans saving?

As you might imagine, the top reason people give for not saving is "having a lot of expenses" at 39%. Another 16% say "their job isn't good enough" and the same amount of people simply say they "haven't gotten around to it." That was followed by 13% who cited "debt" and 6% who said they "don't need to save more."

While 80% of Americans are saving something, according to the report, 67% have failed to save more than 10% of their income. That could be a recipe for disaster.

"With higher incomes coming in because of the tax cut and rising wages, there are ready sources to help fund savings," Hamrick said. "By budgeting for regular expenses and adding a more generous savings component, you'll be paying yourself first."

Which groups are saving?

People who make more money save more money with 20% of workers making at least $75,000 a year saving at least 15% of their income. In addition, having more education seems to lead to saving more with 21% of college graduates hitting the 15% number while those with some college came in at 18%, and workers who are high school educated or less were at just 9%.

"Heavy expenses" was the top reason for not saving across all age groups. In addition, 20% of Millennials (ages 18-37) blamed their lack of savings on the jobs not being good enough while 27% of the Silent Generation (73 and older) said they aren't saving because they no longer need to.

What can you do?

One of the challenges of saving for retirement is that retiring seems like something in the distant future. It may be easier to set short-term financial goals like building an emergency fund that covers six months of expenses. Once you achieve that, hopefully, saving has become something you simply do -- a part of your budget like rent or food.

Saving money for whatever may come can avert disasters like having to borrow at a poor interest rate to cover an unexpected expense. Think of saving from every paycheck as a type of insurance that you may not need today but that you will be very happy to have if the day every comes that you do.