Smoking, driving too fast while yakking on the cell phone, eating ice cream every night of the week ... we all have habits that we know aren't good for us. For some reason we persist anyway, even knowing that we may be setting ourselves up for real trouble.

It's hard to break bad habits, and that goes for financial ones too. The obvious culprits, like overspending on credit cards or overdrawing the checking account, can be annoyingly persistent. Establishing positive habits, like saving regularly for retirement, can sometimes seem harder than resisting the Ben & Jerry's in the freezer.

Why do we stick with these bad habits? Well, scientists have been looking into that, and a recent article in LiveScience reveals some of the reasons they've uncovered. (Scientists have pretty cool jobs, if you ask me.) See if any of these rule your financial world:

  • Innate human defiance. Yep, there's something in people that just wants to throw a tantrum, disobey, and defy authority. Are you ignoring the bank's rules or the credit card payment deadlines just to be rebellious? You might try short-circuiting this problem by reminding yourself that it's in your interest to play by the rules, even if you don't like them. You're only punishing yourself.

  • Social acceptance. In other words, everybody's doing it and we don't want to be left out of the crowd. Think about this one if you're prone to jumping on the latest financial bandwagon. Exchange-traded funds, for example, have been a hot financial product lately. They allow you to get great diversification for very low fees, much like index funds. In fact, some, such as the Standard & Poor's Depository Receipts 500 Trust, or "Spiders," act almost exactly like their mutual fund cousins.
    But ETFs now come in at least 200 varieties, and they may be getting out of control, as fellow Fool Selena Maranjian recently wrote. If your portfolio is packed full of ETFs of all shapes and sizes, consider whether you've lost your focus amid the spectacle of new ETF offerings.

  • Inability to truly understand risk. Evidently, people respond more to explanations of risk when they're presented in emotional terms, rather than in numbers. So, if I tell you that your savings is earning 2.5% interest at a time when inflation is growing at a 3% rate, you might conclude that's pretty good. If, instead, I tell you that all your hard work stashing away an emergency fund is about to be wiped out by the passage of time, forcing you backward in your path to meet your financial goals, I might really get your attention. If you find you're getting lost in the numbers, try translating the figures into sentences that better describe the implications to you.

  • Maintaining an individualistic view that rationalizes unhealthy habits. In other words, the cigarettes haven't killed you yet, and the credit card companies haven't cut off your cards. In a variation on this theme, you remind yourself repeatedly of your Great Aunt Verna who lived happily to age 90 and never paid a bill on time in her life. I, personally, think this is a variation on the first problem -- rebellion. You tell yourself, if someone got away with it, maybe I will too. It's possible, but remember that by ignoring the rules, you're only punishing yourself.

  • Genetic predisposition to addiction. Not being a scientist, I really can't tell you what to do about this one. Maybe trade your credit card addiction for something healthier, like running?

We at least now have a little insight, even if learning all this doesn't actually help us break our bad habits. If you want to enforce some good financial discipline, take a look at the Savings and Retirement centers.

Or check out these other habit-forming articles:

Motley Fool GreenLight can help you turn your bad financial habits into helpful ones. For tips on making the most of your money no matter what stage of life you're in, check it out for absolutely free for 30 days.

Fool contributor Mary Dalrymple welcomes any of your advice for kicking bad habits and other feedback.