You know you could learn a lot from your grandparents, right? You can learn even more from more grandparents -- from a host of senior citizens, in fact. A recent survey of seniors produced a long list of their financial regrets, a list that offers instructive insights.

Check out the regrets below and see which ones are likely to become your own if you don't change some of your ways now.

An older man is looking toward the viewer, with a displeased expression.

Image source: Getty Images.

Survey says...

The survey in question was commissioned by the folks at LendEDU and conducted by Pollfish in March 2018. A thousand people aged 65 or older were asked a variety of questions, and their answers to the question "What is the biggest financial regret you have from your twenties?" are below:

Percent

Response

21.4%

"I didn't save enough for retirement"

17%

"I spent too much money on nonessential things"

12.3%

"I didn't invest my money"

10%

"I got myself into too much debt"

5.8%

"Took a job where I made less money but enjoyed it"

5.5%

"I made poor investment decisions"

5.1%

"Took a job where I made more money but did not enjoy it"

2.8%

"I didn't save enough for my child's education"

20.1%

"None of the above"​

Data source: Lend.EDU. 

Let's take a closer look at some of those regrets.

"I got myself into too much debt"

It may seem obvious to you that we should all avoid getting deep in debt. What isn't obvious, though, is how easy it is to end up mired in debt. One reason is that many (but not all) credit cards "penalty APRs," meaning that if you have one transgression, such as paying one bill late, they can jack up your interest rate to 25% or even close to 30%. That can be a recipe for financial disaster, if it makes your debt grow faster than you can pay it off.

Imagine, for example, that you owe $10,000 on your credit cards, as plenty of people do. (A recent average balance for Americans was $6,375, per an Experian report.) If you're paying a not-uncommon interest rate of 17%, that amounts to a hefty $1,700 annually in interest alone. If your rate gets hiked up to 29%, though, you'll be paying nearly $3,000 in interest, which can make it hard to get much principal paid off.

Some low-interest rate debt, such as a mortgage for a home you can afford, is reasonable. But avoid buying things you can't afford, lest you dig yourself into debt.

"I didn't save enough for retirement"

A key reason that many people don't save enough for retirement is that they simply don't know how much they should save. Take the time to review your financial situation and future needs and expectations and come up with an estimate of how much you need for retirement. That number can help you figure out how much you need to sock away each year.

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Image source: Getty Images.

"I didn't invest my money"

If you're not saving and investing for retirement -- and doing it in earnest -- you may be setting yourself up for a difficult future. Social Security is important, but it probably isn't going to provide as much income as you'd like. The average Social Security retirement check was recently $1,417, or about $17,000 annually. There are ways to increase your Social Security benefits, but even they will only go so far. So aim to build a war chest for retirement that can eventually provide additional income -- perhaps via dividends, or by your selling off shares of stock over time, or maybe via annuity payments.

Here's how much you might amass over time if you're aggressive and disciplined:

Growing at 8% for

$5,000 Invested Annually

$10,000 Invested Annually

$15,000 Invested Annually

15 years

$146,621

$293,243

$439,864

20 years

$247,115

$494,229

$741,344

25 years

$394,772

$789,544

$1.2 million

30 years

$611,729

$1.2 million

$1.8 million

Calculations by author.

"I made poor investment decisions"

Few people are ever taught how to invest, so it's no surprise that many of us don't invest well. Fortunately, you don't need a master's degree in finance to invest well. For most people, it's best to just stick with an inexpensive broad-market index fund, such as one based on the S&P 500, that will deliver roughly the same returns of the overall stock market.

The Vanguard 500 Index Fund (VFINX), for example, tracks the S&P 500 index, which is made up of 500 of America's biggest companies that together represent about 80% of the entire U.S. stock market's value. You can go even broader with the Vanguard Total Stock Market Fund (VTSMX), which encompasses all of the U.S. stock market, including small companies, or the Vanguard Total World Stock Index Fund (VTWSX), delivering the world market. These are examples from Vanguard, but there are more than a few other brokerages or fund families offering low-cost index funds, too -- very possibly including some available to you via your brokerage or workplace. You can also opt for exchange-traded funds, or ETFs, that focus on the same indexes -- such as the SPDR S&P 500 ETF (SPY), Vanguard Total Stock Market ETF (VTI), and Vanguard Total World Stock ETF (VT). If you want to balance out your portfolio with bonds, you can do that via index mutual funds and ETFs, such as the Vanguard Total Bond Market ETF (BND).

If you can avoid having the above disappointments by the time you become a senior citizen, you'll likely have set yourself up for a comfortable retirement. You may lament not having traveled to Europe, but your sizable nest egg might pay your way there. A little planning and perseverance now can minimize your future regrets and put you on solid financial footing.

Selena Maranjian has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.