New Year resolutions: what makes them stick?

From reaching for our phones the moment we wake up to brushing our teeth in the evening, habits shape our everyday lives. It's estimated that nearly half of what we do happens 'on autopilot', out of habit.

Habitual behaviours can be hard to shift, and we can beat ourselves up when we fail to stick to the new changes we want to bring to our lives. Making healthy actions habitual should make them stick, while breaking unwanted habits clears space for healthier choices.

Recent progress in social and health psychology reveals how – and why – we can make and break habits to boost our health and happiness. As a researcher in this field, I've learned firsthand about my own habits; why some changes I've tried have clicked into place, and why others, like resisting late-night snacks, are harder to crack.

So, this new year, when most of us have a resolution we want to stick to (but less than half of us, 45%, manage it) how can we use the latest science on habits to create changes that last?

Habits and habitual behaviours

First, we need to understand what habits are. Psychologists see habitual behaviours as actions we do automatically when we encounter cues we've learned to associate with them. For example, like millions of other people, I reach for my phone (action) as soon as I wake up (cue).

Surprisingly though, there is no agreed definition of 'habit' itself. Neuroscientists, for example, see the action – reaching for the phone – as the habit. But that causes problems for social psychology, where theories depict habit as the cause of action. Habit can't be both what we do and the cause of what we do. Many social psychologists now see habit as the association between a cue and an action. Habit isn't what we do, it's the mental link - between waking and grabbing the phone – that drives us to do it. This subtle difference between habit – a cause of action – and habitual behaviour – the action itself – is key to understanding how habits work.

When habit is not enough

Unsurprisingly, making an action habitual increases the chance that we'll do it when cued. Years ago, I started a habit of exercising first thing in the morning. It wasn't easy at first – waking up earlier took effort, and I often struggled to get out of bed. But knowing what to do and when – a YouTube workout at the start of the day – created a clear and simple rule to follow. And as the research predicts, it gradually got easier to stick to. Now, when I wake up, I feel the urge to exercise; it's just part of my routine.

But separating 'habit' from 'habitual behaviour' draws attention to interesting instances, when habits do not match our behaviour. Habits create powerful impulses – those automatic nudges that push us towards certain behaviours without thinking. For me, waking up now effortlessly triggers me to get changed and head to my workout area. But habit is rarely the only force at play.

We act on whichever impulse is strongest in the moment – and sometimes other priorities create stronger impulses. During busy periods, I've deliberately skipped my morning workout to tackle urgent work. When I've been injured, a wish to avoid anything strenuous has overpowered my exercise habit. Habit impulses may be strong, but they don't always have the final say over what we do.

And if habits don't always translate into action, then we must question whether forming a habit really makes a behaviour stick. Habits are supposed to keep us consistent, but higher-priority impulses can knock us off course. In theory, after years of daily activity, missing a workout on one day shouldn't affect the strength of my habit. But in reality, I'd see a missed session as a major setback. That small stumble would knock my confidence, weaken my resolve and start a slippery slope back towards my old, less active ways. 

So, is forming a habit the key to behaviour change, as many applied psychologists believe? Well, if you are trying to do something new, forming a habit will certainly help. But success may depend on having back-up plans for when habit is not enough. The only way I've kept my streak going is by mindfully planning sessions later in the day, when my morning exercise habit was not the strongest impulse.

'Habitually deciding' and 'habitually doing'

Some psychologists question how habit can apply to complex human behaviours. After all, much of what we know about habits comes from lab experiments with animals. Can the same mental process that drives a rat to repeatedly press a lever really help us keep exercising or eat healthily? We think this can be resolved by distinguishing between the two roles habit can play in any behaviour.

Take another of my habits: making a cup of tea when I get to work. This may seem like one habit, but there's a whole chain of habits at play here. One habit kicks in as soon as I arrive: getting to the office cues me to grab my mug and head to the kitchen. From there, several further habits help with the finer details. Associations between arriving in the kitchen and grabbing the kettle, and between grabbing the kettle and filling it up, for example, ensure I make a decent cup of tea even when I am not paying attention.

Habits that determine what we do – making tea, rather than, say, getting a glass of water, or checking email – are what we call 'instigation habits', and these help kickstart the sequence. The finer-grained habits that shape how we do what we do – pouring boiling water after adding the teabag, rather than adding the teabag to boiling water – can be thought of as 'execution habits'.

Building chains of execution habits helps us master everyday actions, and frees us to think about more important things, like the day ahead. But instigation habits, not execution habits, are what make us repeat our everyday behaviours. We're more likely to, for example, exercise, floss, or eat breakfast if we create associations that help us 'habitually decide' to do so. Whether we 'habitually do' the same exercises each time, floss in the same order, or eat the same food each morning is less important.

Habitual instigation: a simple way to make complex changes

Instigation habits can spark even very complex actions. Like many Londoners, for example, my morning commute starts on autopilot, cued by dropping my kids off at school, even if navigating the underground at rush hour requires some mental gymnastics.

Habits may not fully control every step of a complicated task, but having a habit that triggers us to start doing something – whether tying your running shoes or opening your laptop to start writing – can encourage repetition of both simple and complex actions. Psychologists often advise people to form habits by repeatedly doing the same thing in the same way in the same setting. But these new insights offer more precise, nuanced – and simpler – habit advice. 

If you're trying to take up a healthy behaviour, like exercising, focus on forming a habit that gets the action started. Creating a habit for heading to the gym after work will increase your chances of exercising - but you don't have to do the same exercises in the same way each time. In fact, doing the same workout each day can make working out dull, and may discourage long-term change.

How to break bad habits

Understanding the difference between habits and habitual behaviour is key when it comes to breaking those bad habits that just won't budge. One of my own unhealthy habits – which I have admittedly rather less success with – involves eating sweet treats late in the evening. My colleagues and I have identified four types of strategy that are recommended for breaking bad habits like this.

One strategy, which we term 'habit cue discontinuity', involves avoiding triggers altogether. Maybe I could go to bed earlier, to dodge the temptation to snack in the evening. Another strategy – 'reducing behavioural accessibility' – involves making the unwanted action harder to do. If I stop buying sugary treats, they won't be within arm's reach when the impulse kicks in. A third strategy – 'habit inhibition' – involves simply trying to resist temptation. When I find myself opening the snack cupboard, I could remind myself why snacking isn't worth it, shut the cupboard, and walk away.

I've tried all these strategies in some form or other, but none worked over the long-term. I don't always want to go to bed early, my wife does the shopping, and trying to stop myself snacking just made me think about snacks. I'm not alone in finding these strategies unsatisfactory. They often fail because they target habitual behaviour, not habit. They aim to stop us acting on habit impulses, but don't tackle the associations that create those impulses.

Even when we stop ourselves acting on our bad habits, those habits can lie dormant – and can resurface when we're too tired, stressed or distracted to fully control our actions. For example, our research showed that even people who changed their diet and kept the weight off for over six months struggled with their old habits (Gardner et al., 2021). External stressors, like family issues, often pulled them back into unhealthy ways despite months of progress. That fits my experience. I've stopped my evening snacking for months on end, but then a stressful episode, like a heavy workload, prompts a lapse, and it's back to the biscuit tin.

In theory, the best way to break an unwanted habit is through 'habit substitution' – replacing an old, unwanted response with a new, better one. Instead of simply resisting temptation, this strategy focuses on consistently doing something else in place of the unwanted response. Although late-night snacking is never advisable, I could try eating, say, fruit with yoghurt instead of chocolate biscuits. Over time, if I can repeatedly choose fruit, the new healthier habit will override the old one, creating a new default that's easy to stick to. "Alexa, add some yoghurt to the shopping list this weekend".

How to make and break habits

Working in habit research has helped me understand what I do, why I do it, and how to make healthy changes of my own. While I still have plenty of progress to make with my own routines, I offer three pieces of advice to anyone wanting to use the science of habit to make lasting changes.

• Be realistic about what habit formation can achieve. Building a habit makes it far more likely you'll stick to your chosen activity. But it's wise to have a backup plan. If your morning meditation routine falls through, knowing where to fit in a quick session later on will keep you on track.
• If you want to form a new habit, focus on automating the 'decision' to act, so you get started without thinking. If you want to go running, build a habit that gets you changed into your running gear. At the same time, allow yourself some flexibility to keep your run fresh and interesting. Running new and different routes, or varying your pace, will keep you motivated. 
• To break an old habit, avoiding triggers, making the action harder, and trying to catch yourself in the act are all sensible suggestions. But the underlying habit often lies dormant, and may reemerge when your willpower dips or you're distracted. Try to replace an old habit with a new one that can directly and realistically compete. If you routinely eat snacks at your desk during your mid-afternoon dip, try eating fruit or having a glass of water instead. Over time, your new healthier habit will take the place of the old one, and you'll be reaching for the fruit bowl without a second thought.