Back in 2008, San Diego native David Bruno decided to reduce his personal possessions to exactly 100 items, and live with just that many for a year. By the time the recession was in full swing, his "100 Thing Challenge" had inspired a host of other consumers to do the same. Some have taken the idea further, to just 50 things.

Around the same time Bruno was launching his contest, Cathy Erway of Brooklyn, N.Y., was winding up a two-year stint of cooking for herself daily. The author of "The Art of Eating In" had sworn off eating food from New York City restaurants (including take-out) to avoid wasting money on what she called unsatisfying food.

In the struggling economy, such financial experiments have become a popular way not just to save money, but also to curb the constant drive to spend, buy and consume, says Paula Peter, an assistant professor of marketing at San Diego State University s College of Business, where she teaches courses on consumer behavior. "People are more aware of their consumption, and anti-consumer waves," she says.

That attitude has drawn more consumers to challenges such as Six Items or Less, a movement to wear just six articles of clothing in various combinations for a month, or A Dollar A Day, which limits grocery spending to that figure.

Bruno and Erway's challenges prompted long-term changes to more frugal lifestyles. Erway's time dining in cut her weekly food budget from $100 to roughly $35 and taught her how to shop wisely and make the most of leftovers. Bruno cops to owning "probably 105, 110 things" at this point but says maintaining a set number of possessions led to more thoughtful spending. "We don't just go to the mall on a whim and spend $50," he says.

However, a drastic financial challenge doesn t necessarily lead to sustainable new habits.

"A lot of what s going on has parallels to fad dieting," says social and behavior psychologist Matt Wallaert. "Cheap is cool right now, and being frugal is trendy." Approach one of these dares in the wrong way, and you re likely to bounce back into bad habits -- and even spend more than you did initially, he says.

Here's how to tackle financial challenges in a way to make them stick:

Get excited. "You have to find a challenge that jazzes you," says Gail Cunningham, a spokeswoman for the National Foundation for Credit Counseling. If the idea of visiting Craigslist and thrift stores instead of the mall for a year leaves you cold, a challenge to buy nothing new is probably not a good fit.

Look long-term. Ask yourself what happens after you ve successfully passed a month spending $1 a day on food or wearing only six items from your closet, Wallaert says. "Make sure the end goal is something permanent," he says. The challenge will be more meaningful if it teaches you a lasting lesson, like how to be a better coupon user or why to buy only versatile items of clothing.

Keep in mind the goal may not be purely financial. John Perry started The Compact in 2006 with friends and neighbors in San Francisco to embrace habits that helped them reduce, reuse and be more sustainable. "It s really a green thing, not a money green thing," he says. Now in its fifth year and with a national following, the group has found plenty of alternatives to buying things new. Frugality is the side effect, not the goal.

Don t fixate on the numbers. Although many challenges focus on limiting yourself to a set number of possessions or expenditures, the correct figure should be one that s livable for you, Bruno says. "I just happened to have a decent life circumstance where 100 was the right number for me," he says. "Be gracious to yourself. This is not some sort of austerity program." (Bruno's 100 things include a few groups -- books count as one item, as do multiple pairs of socks and underwear -- and exclude shared household items. He made sure to leave in a few fun items, such as a surfboard and camping gear.)

Recruit others. Public commitment to a financial challenge is important -- and not just because embarking on a large-scale possession giveaway is a psychological red flag, Wallaert says. Letting other people know you re not buying new things or eating at restaurants helps them offer support in tempting situations. Sharing a goal can also make it more attainable, Perry says. "We [Compact participants] borrow a lot, and we share a lot," he says. "It was always meant to be fun and competitive."

Do a trial run. Going cold turkey into a challenge for a short period can help you figure out if it's workable long-term. "People jump into these challenges with both feet when they should just put a toe in to see what the water is like," Cunningham says. "Go 30 days and see how you do." Erway says even a week straight of cooking at home helps people form a routine and reduce the waste from leftovers left to go bad. "When things are in constant rotation, being used, eating in all the time is a lot more manageable," she says.

Take small steps. Once you ve tested a challenge, make small reductions each month to find that workable level, Peter says. "It s absolutely not about restricting yourself too much, too fast," she says. Like a grapefruit-juice-only diet or a too-tight budget, you re more likely to bounce back into old bad habits if you feel deprived enough that the first obstacle derails you.