We hate to tell you this, but it’s unlikely that 2015 will be the year you double your salary, run for two hours a day, see the world, stop drinking and never touch processed sugar again. But you can make resolutions that will change your life for the better. Here’s how.

Be realistic about what you can achieve

When you’ve been sitting on the sofa in a crumb-covered slanket for eight days and the self-loathing starts setting in, you may feel that an extreme lifestyle change is required. We’ve all looked down at our distended stomachs, suppressed a tear and thought: “I know! I’ll spend the next year training to cycle up Mount Kilimanjaro, while eating only steamed chicken. That will fix this mess.” But wellbeing expert Tiffany Morrison warns: “If your resolution doesn’t fit with your current lifestyle, it’s over before it starts. There’s no way to overhaul everything at once. It’s much better to make a small change: the less you notice your schedule being disrupted, the more you’ll notice the positive impact.” Try a once-a-week cycle ride, and if that goes well you can head to the mountain in 2016.

Pick something positive

Poor January has a reputation for being a month of misery and self-denial, as everyone settles to a list of “I will nots” and “I will nevers”. “Willpower is a muscle,” says behavioural expert Denise Cummins, “and you have to strengthen it slowly in order to nurture it. You’ll damage its effectiveness through overuse.” If all your resolutions are based on resistance, you’re setting yourself up to snap. “I will eat one meal a week that is entirely vegetable” is more likely to stick than: “I won’t ever eat cake again.”

Be super-specific

A resolution should focus less on the end goal than on how you intend to achieve it. “‘Lose 10lb sounds specific,” explains psychologist Andrea Bonior, “but it’s less likely to work than behavioural goals like: ‘This week I’ll try to go to the gym three times, take the stairs at work at least twice, and bring a healthy lunch every day.’” Give yourself a game plan. If you don’t know how you intend to achieve your goal, you’ll find yourself making the same resolution next year.

Avoid the ‘wrong’ resolutions

Resolutions are like winning reality shows – to be successful, you have to really, really want it. Life coach Mark Dowling says: “If you’re under unreasonable pressure, whether it’s from your friends, family or colleagues, you may make a resolution that will impress them, rather than one that’s right for you. Your happiness should always be the end goal. If someone has made you feel like you should lose weight for your wedding, or that you must save up for a group skiing holiday, but you don’t actually want to, then the resolution won’t stick. You’ll let yourself down if you don’t put yourself first.”

Prepare for bad days

Human nature means that there will be some backsliding. At some point you’re going to crack, either because you’ve had two virtuous months and you’re desperately bored, or because the whole thing seems so daunting that you feel like giving up on day three, when your New Year hangover has cleared and you’re back on solids. “Be kind to yourself,” says Dowling. “You’re learning a new way of living, which is going to take time, and you can expect to make mistakes. Breaking the resolution is only a problem if you then think: ‘I might as well give up.’ Know that it’s OK to fail sometimes, as long as you keep trying.”

Don’t make too many

It’s tempting to fill a notebook with resolutions, colour-coded according to genre and cross-referenced with Post-its – but it might be easier simply to resolve to buy less stationery.

“There’s a sense that a resolution has to be grand and life-changing, but essentially it’s just a to-do list,” says Amy Canning, a careers coach specialising in efficiency. “When you start a day with 20 or 30 things on your to-do list, you’re never going to get to the end of them – and you’ll end the day feeling as though you failed, rather than taking pride and pleasure in what you have managed to achieve. Aim to do less, and do it better – I’d advise a maximum of three resolutions, five if you absolutely must.”

Remember your greatest hits

With many apologies to Charles Dickens, it’s a far, far better thing to think of all that you have done than to think of all that you have to do. Make a list of everything you’re proud of achieving in the past – all the projects that have challenged you, that you’ve seen through to completion. It could be a work assignment, a difficult house move that made you think it might be easier just to live in a tent in the park, or a dinner party where you managed to serve everyone food despite being tempted to set fire to the kitchen and flee the scene. If you’ve ever managed to finish something that you started, you’re strong enough to keep a new year’s resolution; this happy thought can help you on your way to success.

Take your time

After Christmas, the odds are never in your favour. It’s cold and dark and wet. You’re probably broke. There is no month of the year in which you will have a greater desire to stay at home and eat pies. Think of January as a pre-game month. You can ease yourself in, and make sure you’re ready to start a new regime in February, or even later. Personal trainer Jamal Dawson says: “I have an overwhelming number of new clients in January, but less than half of them are still with me by March. I think my best retention month is September – people have told me that, long after they’ve left school, that month still feels more like the start of a new year to them, and they have more energy when it comes to trying new things.”

Daisy Buchanan tweets as @NotRollergirl