Setting reasonable goals would help people monitor progress, Ms Marsters said.
New members were also advised to check in with a trainer to ensure they were on track.
But complementary goals around nutrition and diet were also important, Ms Marsters said. "We always say 80 per cent of it is diet, so you can work out until the cows come home but if you're putting the wrong stuff into your mouth, it's not going to work."
Meanwhile, Mr Wilson warns that sweeping goals, made in a post-party haze, are likely to fail once people return to everyday work.
"A lot of our behaviour is controlled by the environment [and] many of the things we think of as habitual happen in particular situations."
For example, many people found it easier to quit smoking when on holiday because the "usual environmental cues" weren't there.
But once home and back into their old routines, they often started again, he said. He advised smokers wanting to kick the habit to identify what triggered them to smoke.
Whether it was stress, or a certain activity - for example lighting up after work - people would have a better chance of succeeding if they found something else to distract them from smoking.
So when you were setting goals or drafting ambitious New Year's resolutions, it was important to plan for "slip-ups", Mr Wilson said.
Rather than honing in on a single overarching goal, set a complementary resolution that will help you achieve that goal.
For instance, taking up an art class or going to the gym after work will distract someone who takes to smoking or eating unhealthy food at the end of their working day.
Goals also have to be reasonable and achievable, Mr Wilson warns.
"Breaking a goal into stages is good because it means, first, you know what you need to do and secondly, that failing at one small step doesn't necessarily mean going all the way back to the start."
That way if someone slips up, they can go back a step, rather than failing entirely.
Mr Wilson also warned against being too generous with rewards. "Some people are better able to stick to goals than others - it's related to the personality characteristic of conscientiousness.
"The more conscientious you are, the more likely you are able to make goals and stick to them," he said.