It's a burst of dogged determination that experts say is too often abandoned before the last of the holiday shortbreads are eaten.
Oh, well, there's always next year.
"Definitely people are motivated in January," says Sandra Jamieson, program co-ordinator for the Tower Athletic Facility at Saint Mary's University in Halifax.
"I try to encourage that and get people to remember what got them started in the first place because some people tend to lose that motivation in a few weeks."
Janet Polivy has been studying the notion of self-change through diet and exercise for the past three decades. Specifically, why is it that people don't seem to learn from their broken commitments, no matter how many times they've given up on the same promise?
"It started to strike me as something very odd," says Polivy, a professor of psychology and psychiatry at the University of Toronto at Mississauga.
"We are supposed to learn from our mistakes, and what we seem to learn is how to make them over and over again."
Her research has shown that despite fitness failures, what chronic resolution-makers tend to remember the most is their success, no matter how brief. And Polivy says everyone has at least some degree of success with a new resolution.
"You can do any self-change for at least some time ... but then it gets hard," she says. "There aren't immediate benefits that you can see. You don't get a big payoff."
It's something Polivy has coined "false-hope syndrome" — the mistaken idea that self-change efforts will lead to a huge and fast reward. It's that hope that creates repeat offenders.
Craig Saikaly, vice-president of operations for GoodLife Fitness in Atlantic Canada, says keeping people motivated and realistic about their goals is a year-round challenge, but particularly so around the beginning of the new year when more people are signing up for memberships.
"People who get started in January are often so optimistic about what it is that they want to accomplish," he says. "They're really fired up for a month or maybe two."
When change doesn't come fast enough, Saikaly says disappointment tends to set in and newcomers are at risk of falling off the workout wagon.
Polivy agrees, but she says it's not surprising they are often enticed to try, try again.
She points to advertisements featuring happy, smiling exercise enthusiasts and quick-fix miracle machines that vow to tighten and tone in little time, with minimal effort.
Such ads may set up couch-potatoes for disappointment, but Polivy says no one is doomed to a life of broken resolutions.
She suggests finding a type of exercise that you don't mind doing — even if you don't love it. Maybe hitting the gym isn't your thing, but a fast-paced tennis match is.
Most important is setting realistic goals that can be measured, and determining what actions will help you achieve that goal. Ultimately, a major part of success is accepting that nothing happens overnight.
"If you're going to change, you have to be prepared to face the fact that this is a permanent change," says Polivy. "People make a resolution, but it's usually time-limited."
At the Tower, Jamieson says working toward a specific event, such as a marathon, a wedding or an upcoming vacation, tends to motivate people to get in shape because there's a date looming.
For some gym-goers, Jamieson says staying on track comes down to the bottom line. No one likes to see their membership dollars wasted from one month to the next.
"For some people, I notice that is motivating and it does get them to come in and continue," she says.
Saikaly says GoodLife offers a variety of group exercise programs at different levels to keep people interested and challenged. Members can also sign up for personal training as an individual or in a group, which can provide the accountability some people crave.
There are group orientations for first-timers to get comfortable in a gym setting and learn how to use unfamiliar equipment. There's also the social aspect of working out, which Saikaly says can make exercise feel like interacting with friends.
Often, Saikaly says success means realizing that changing your habits doesn't mean rearranging your entire life. Forty-five minutes of activity, two or three times a week, is plenty.
"If you can just do those small baby steps over a long period of time, you're going to always see gradual results, you're always going to feel great," says Saikaly.
"You're not going to want to leave."