Bad Habit No. 5: Using retail store credit cards to take advantage of discounts 

Chances are that card carries a high interest rate you'll be forced to deal with if you don't pay off your balance each month.

Try this: If you must charge your purchase, use your general purpose credit card, says Cunningham. If you can't pay off the balance, at least you'll pay a lower interest rate. Limit the total number of credit cards you have to two, if you can: one you can pay off each month and one with a low interest rate for those large purchases you'll pay back over time.

Bad Habit No. 6: Procrastinating on creating an emergency fund 

Learn to save for financial emergencies. Even if you feel robust and invincible, a single emergency room trip or car accident could force you to put large balances on credit cards, causing interest to accrue and more debt to pile up.

"That rainy day will happen," Cunningham says. "It's not a matter of if, it's a matter of when." If your tire goes flat and you can't pay upfront for the replacement, for instance, you're stuck with charging it or reducing funds earmarked for necessities. That's where the emergency fund fits in.

Try this: Maintain an emergency fund of at least three to six months' worth of living expenses and keep your insurance plans up to date. Work toward that goal by socking away 10 percent of your take-home pay each month in a liquid savings account, says Cunningham. If you receive a raise or bonus, add that money to savings. Since you're not used to the extra cash flow, you won't miss it.

Bad Habit No. 7: Pay bills in no particular order 

While the order may not matter if you can pay all the balances, it will matter if you fall short one month. Say you pay off the balances on your credit cards first, and then find you can't make the minimum on your house payment or monthly rent. You've put the roof over your head at risk.