3 of the Worst Millennial Money Habits These habits are worth breaking -- now.

Bad habits are easy to fall into—especially when you're in your 20s. Some of the worst money habits among millennials, according to recent surveys include overspending, undersaving and racking up credit card debt.

One in 5 millenials hasn't even started saving, according to a recent USA TODAY/Bank of America Better Money Habits poll. Three in 10 don't even have savings accounts! And of those who do, nearly 40 percent have less than $5,000 saved. And when it comes to putting money aside for long-term goals like retirement, the numbers are just as bad. A 2014 Fidelity survey found more than half of millennials had yet to start saving for retirement. In fact, that was the top issue that the millennials surveyed said they were trying to tackle. The next? Paying off credit card debt.

No surprise then that almost 4 in 10 of the millennials surveyed by Fidelity admit to worrying at least once a week about their financial future. The good news: It may not be as hard to break those bad habits as you think.

1. Track your spending

He notes that many get tripped up by weekend purchases on a debit card, which may not post until Monday. Unless people are tracking their spending carefully, they may believe their balance is higher than it is and overdraw their account. According to data from a Consumer Financial Protection Bureau report, 1 in 10 millennials overdraft more than 10 times a year. That can add up to $350 or more in overdraft fees!

Charles Sachs, a certified financial planner and accountant in Miami, recommends using the spending log and other tools in the "Building Wealth" online guide, created by the Federal Reserve Bank of Dallas, to track your spending and create a budget.

2. Plan ahead for big expenses

Putting a big expense like a vacation on a credit card can be risky—even if you think you can pay it off soon. Interest adds up quickly. And if an unexpected expense comes up and you're late or miss a credit card payment, you can get hit with a penalty fee and a higher interest rate on the balance you owe. A late or missed payment can also hurt your credit score, which can make it harder to get a loan (or a good rate on a loan anyway) down the road.

Sachs recommends adding a line to your budget for big upcoming expenses like vacations. You can set up a savings account and have money automatically transferred into the account from your checking account, or from your paycheck if your employer allows it. Just check to be sure that you won't be charged a fee for the savings account, and that there is no minimum balance requirement.

3. Set up an emergency fund

Sachs also suggests setting aside money in a rainy day or emergency fund. How much? Financial experts typically recommend saving enough to cover three to six months of nondiscretionary living expenses like rent, utility bills and car payments. That way you'll be prepared if you get hit with an unexpected expense or lose your job, and you won't have to turn to your credit cards—or your parents—to cover your bills.

Setting up an emergency fund can also help you get into the good habit of saving money for your future. The more money you save, the easier it will be to keep from falling back into bad habits.