The right attitude was also important: Those who rewarded their successes and avoided self-blame for slipups had resolutions with more staying power.
"Successful people had the same number of slips early in January as people who would ultimately be unsuccessful, but it was how one dealt with those slips" that mattered, he says.
But even though more than half of serious resolutions fail before the spring, there's still value in making a resolution, Norcross says.
Only 40 percent of resolvers in Norcross' study succeeded. But those who had a behavior they wanted to change and didn't make a New Year's resolution succeeded only 4 percent of the time, he points out.
Considering the difficulty associated with keeping resolutions, it should come as little surprise that these hopeful promises are a subject of curiosity for many researchers.
What they have found is this: The resolutions we make are tied to a region of our brains known as the prefrontal cortex. And because this high-traffic area handles other important functions -- including emotion and complex thought -- our resolutions tend to fall by the wayside if we are distracted by other matters, according to researchers.
Take, for example, the research of Baba Shiv at Stanford University, who in 1999 conducted a novel experiment in which two groups of students were asked to remember either a two-digit number or a seven-digit number. During this task, the students were presented with a choice -- either have chocolate cake as a snack, or a bowl of fruit. Those who were charged with remembering the longer number were far more likely to choose the more decadent dessert.
In other words, when it comes to the high demands of daily thinking, resolutions all too often take a backseat.
How you phrase the resolution plays a vital role in your ability to carry it out, blogger Rubin says.
"People need to be very, very concrete ... something like, 'Enjoy the moment' or 'Be optimistic,' how do you do that? People don't know how to keep that."
Rubin also points out that it's important to be sensitive to the positive or negative spin your resolution has.
"Some people do not like to be told no. They don't like limits ... and they will inevitably resist that type of change," he says. "If you're like that, you need to think about it in a way that feels like a yes to you: Eat more salad instead of no more dessert, for example."
Also, make the resolution small enough to handle, Rubin says, because "a lot of times people make the mistake of setting a really ambitious goal because they are excited about the idea of change. But it's easy to become overwhelmed and be worse off than when you started.
"People overestimate what they can do immediately and underestimate what they can do in the long run," he says, so don't expect big change to happen overnight or even in the first month or two.
Norcross agrees. "It's a marathon, not a 100-yard dash," he says. "This is not just January, this is for life."
But with the focus on self-improvement, people may overlook how much improved relationships can add to their health and happiness, says Michelle Weiner-Davis, divorce counselor, author and founder of divorcebusting.com, an online resource for people with marriage difficulties.