A new day dawns. You’ve resolved for the umpteenth time to cut out the Big Macs, cut back the mindless TV, update your Quickbooks and feed the guinea pig on time.

You’re going to lose 10 pounds, learn to play the five-string banjo and write the great American novel. Today is the first day of the rest of your life! You betcha!

There’s only one problem with such resolutions, which usually start on a Monday morning and rarely make it to Tuesday afternoon. It’s that habit almost always trumps resolve, and the road most traveled is usually the path of least resistance. Soon you revert to form, and spend each night dozing in your Barcalounger, a half-eaten burger in your hand, with reruns of American Idol flickering on the tube.

If you want to change your life but can’t seem to make change last, consider a “commitment contract.” The idea came from a Yale University economics professor named Dean Karlan who contracted with a buddy to lose almost 40 pounds each. To do it, the friends put a high price on failure: whoever did not achieve his goal would forfeit half his annual salary. The men were serious, and each achieved his goal weight in the time allotted.

To stay fit, they renegotiated the contract, and when Karlan’s pal gained weight, he was obligated to fork over $15,000!

“Had I refused to accept it,” observed Professor Karlan, “no future contracts would ever work.”

Karlan went on to found stickK.com, an online “commitment store” that enables people to set their goals in a public forum, set the stakes and the deadline, choose a “referee” (the person who will monitor their progress) and finally, choose who will get the cash if they fail to meet their goals.

In an interesting and perverse twist, Karlan and stickK.com co-founder Ian Ayres suggest that participants choose a cause or entity they do not support, for even more motivation. For example, a person who opposes gun ownership could pledge his money to the NRA, or someone burned in the Wall Street meltdown could throw some dough at the Bernie Madoff Defense Fund.

As the website states, “Wouldn’t it just kill you to hand over your hard-earned money to someone you can’t stand?”

The theory at work here is that incentives, especially financial incentives, can help people stay on track in cases where willpower alone has failed. The Journal of the American Medical Association agrees that the prospect of losing money (or gaining it) is a significant incentive for dieters, especially when the money was not rewarded until the end of a set period, “because people just don’t like to lose money.”

Though weight loss is far and away the most common objective, goals range from learning to play poker to not spending from a savings account to learning more about political candidates.

So, what’s on your goal list? Want to run a half-marathon, learn to square dance, stop using profanity or spend more time with the kids? Put a contract on yourself—on stickK.com, with a pal or with an office group. To really succeed, sometimes you have to put your money where your mouth is.

By Maya Mariner