3 Money Mistakes That Will Come Back to Haunt You

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It was an all-you-can-eat buffet, costing around $12.95, as Mim King recalls. About 10 years ago, King, a professional organizer and money manager in St. Paul, Minn., learned that one of her clients had gone to a restaurant, and he was determined to eat all he could.

"He stayed beyond what most people would consider a reasonable time, simply in order to eat," King says. Before the day was over, his family took him to the hospital to get his stomach pumped. King never learned the cost of the hospital bill, but she is betting that it far exceeded her client's meal.

Everyone makes money mistakes, but if there's a theme connecting many of them, it's that if we stopped and thought about it, we'd realize what we're doing isn't going to end well. While King's client didn't predict he'd wind up in a hospital, if he had thought through his plan beforehand, he might have left after, say, the third or certainly the fourth helping.

[Read: 5 Financial Decisions That Sound Smart But Are Really Dumb.]

In that spirit, here are a few common money management mistakes – and why these decisions are likely to haunt you.

Going to Graduate School Without Thinking It Through

Why it will come back to haunt you: Graduate school isn't cheap. Price tags are all over the map, ranging from a relatively low $21,000 a year for business school at Brigham Young University's Marriott School of Management to $63,200 a year at Harvard Business School. The last thing you need is to graduate and realize you really aren't cut out for your new career.

The consequences: That realization is not uncommon. Shane Fischer, a criminal defense attorney in Winter Park, Fla., says he sees it all the time. He knows many lawyers who hate what they do "but went to law school because they hadn't 'found themselves' at 22. They racked up $100,000 to $200,000 in debt before their 25th birthday. Unless they hit the lottery or get lucky with a big case, their student loan debt will be an albatross around their neck for the rest of their careers, as they will never make enough money to bounce back from the debt as well as the lost income from taking additional years off to go to school."

Which may not be so bad if you love what you do. But if you hate it, the decision will plague you, quite possibly for the rest of your life.

Taking Out an Expensive Loan You Can't Afford

Why it will come back to haunt you: Maybe you'll be able to pay it back, but if you're honest with yourself, you probably won't. After all, the reason the high-interest loan you're considering is so expensive is that you had trouble paying back the previous loans you've taken out. How is this one going to be any different?

The consequences: Desperate times, as they say, call for desperate measures. But some loans are so punishing that desperate consumers would be better off taking whatever lumps are coming to them.

While some credit cards have exorbitant interest rates, and payday loans are well-known as an expensive way to borrow money, among the worst of the worst are car title loans.

The Center for Responsible Lending reported earlier this year that approximately 7,730 lenders give out $1.6 billion in car title loans every year, and to get that money, consumers spend $3.5 billion a year in interest. It's a form of predatory lending that is illegal in about half the states, which says a lot.

[See: 10 Savings Strategies That Can Backfire.]

Here's how it works: A typical borrower receives cash equal to 26 percent of the car's value and pays 300 percent APR. If consumers don't pay back what they borrow, they lose the car. Because most people are determined not to let that happen, they renew the loan – paying back only the monthly interest and renewing the loan for another 30 days. Consumers who borrow $950 typically take eight months before paying back the loan and spend more than $2,140 in interest.

Failing to Save for Retirement

Why it will come back to haunt you: The reasons are obvious: Nobody wants to find out what happens when you have to choose between buying food or medicine.