This is Americans' No. 1 financial regret—and it could be costing them thousands

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Looking back on their finances, Americans wish they had started preparing for the future earlier in life.

That's according to new data from Bankrate, which polled U.S. adults about their financial regrets. Not saving for retirement early enough is the most common regret. Not saving enough for emergency expenses comes in second.

Taking on debt seems to be a lesser concern, according to the findings. Only 10 percent of respondents cite too much credit card debt at their biggest regret, while 8 percent wish they could remake their student loan decisions.

Lack of savings does appear to be a serious, ongoing problem in the U.S. Northwestern Mutual's 2018 Planning & Progress Study found that 21 percent of Americans have nothing saved at all for their golden years, and a third of Americans have less than $5,000.

Forgoing contributions to a retirement fund could be costing Americans hundreds of thousands of dollars each. If you put $5,500 per year, the maximum annual amount, into a Roth IRA starting at age 25, it would be worth around $900,000 by the time you're ready for retirement, assuming a 6 percent rate of return. Contributing just $200 per month, or about half the IRA max, would still yield nearly $400,000 by age 65.

Americans aren't just lacking in retirement savings. Many don't have rainy day funds in place, either.

"In the here and now, most adults do not have enough stowed away in a savings account to adequately protect them from going into debt, should disaster (lost job, health scare) occur," the survey says.

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Even if you already have debt, prioritizing contributions to an emergency fund can prevent a broken-down car or unexpected hospital visit from putting you in a much deeper hole. Building a solid emergency fund before attending to other financial goals, such as paying off debt, is crucial because it prevents bumps in the road from completely derailing the journey, explains Dave Ramsey in "The Total Money Makeover."

And, in order to get ahead on retirement, experts recommend beginning to save as much as you can as early as you can.

"Time is your greatest ally when saving for the future," Greg McBride, CFA and chief financial analyst at Bankrate, says in the report. "To workers of all ages, there is no better time than the present to increase your 401(k) contribution or fund an IRA."

Anyone looking to lower their expenses can consider downsizing their home, trimming their grocery bill or making it a priority to eliminate debt. And those with the capacity to take on additional work can bring in extra cash by renting out spare rooms, reselling items online or taking on freelance work. Here's how much the most common side hustles pay.

Don't miss: Here's how much Americans have saved for retirement

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