Most of us have, at some point in our lives, looked in the mirror and decided we need a radical image overhaul – especially in January. Then, when we don’t achieve the desired six-pack within a month, we tumble off the fitness bandwagon. But is there a way to set realistic, useful fitness goals that will keep you motivated as the nights draw in and the prospect of an extra hour in bed trumps a workout?

First of all, think about the goals not to make – keep in mind that exercise alone won’t change your body shape. If you are looking for major fat loss, you will have to look at diet, too. “People underestimate the amount of effort physical transformations take,” says Hannah Lewin, a personal trainer. She advises clients to focus on positive fitness goals instead – running 5km or deadlifting 30kg – rather than aesthetic goals that will require drastic lifestyle overhauls.

Next, consider what is important to you. “A lot of people come to me and say: ‘I want to look like this,’” says Lewin. “That’s where a lot of goals go wrong from the outset, because you’re choosing a goal based on someone else.”

The personal trainer Ruby Tuttlebee advises starting small and building up. Something straightforward, such as a press-up, is a better bet than aiming for a triathlon right off the bat. She also suggests having a series of goals. When you have mastered a perfect press-up, set a new goal of five press-ups in a row, then 10, then 20.

Lewin agrees: “The first goal should be easy. In terms of a scale of how likely you are to achieve that goal, it should be a 9/10. Progress it from there.” The main reason people fail is that they focus on the thing they want to achieve and become dispirited when it takes longer than they expected. “Focusing on that end goal can be problematic.”

Choosing something you enjoy will help. “If you don’t like something, you won’t give 100%,” says Tuttlebee. Training with a friend or a personal trainer can also keep you on track, when your motivation slips.

Keeping score is also a good idea. “When I set goals with athletes, I look at three types of goal,” says the chartered sports psychologist Helen Davis. Outcome goals are big-ticket achievements, such as running a marathon. A performance goal sits below that and helps you assess whether you are on your way to your outcome goal. Progress goals are day-to-day activities, such as training three times a week or optimising your nutrition. “Monitoring these goals gives people tangible things they can work on and helps direct their focus to keep them on track day to day,” Davis says.

Always reward yourself for achieving your goals, however small. “Even if just walking through the door of your gym is your first goal, you’ve achieved it – so well done,” says Tuttlebee. Above all, remember that your goals are yours alone, she says. “Make it your own. Tailor it to you.”