To say that 2020 wasn’t the best year is an understatement. For many of us, it felt like a giant global dumpster fire. Not surprisingly, the stresses of living through a pandemic have had a terrible impact on our collective mental health, with rates of depression and anxiety skyrocketing. Many of us feel we can’t say goodbye to last year fast enough.

And that means we’re entering 2021 with high expectations. With the promise of a vaccine and the potential for a return to normality, the start of this year has given us something we’ve been missing for a long time: hope. Starting over after the year we’ve just had feels more exciting than usual. It’s a brand new chapter in our lives, in which lots of positive changes are possible.

Research shows this collective new year optimism provides a powerful opportunity to change our behaviour for the better. University of Pennsylvania psychologist Katy Milkman and others have shown that people are more driven to tackle new goals at shared temporal breaks than at random times of the year; something she calls the “fresh start effect”. Whether it’s a birthday, the first day of school or even a Monday morning, fresh start moments give us a boost of motivation by focusing our attention on the big picture and what we really want out of life. They make us feel less weighed down by past mistakes, as if we’ve been given a blank slate. But if we don’t approach our goals wisely, resolutions can do more harm than good.

If you’re like most Britons, you’re probably planning some self-improvement this month. For many, the new year feels like a good time to overhaul our bodies, finances, routines and relationships. We focus our attention on all the ways our circumstances and past behaviours suck, and we assume the best way to complete that big life overhaul is with some serious tough love. We channel our harsh inner drill sergeants. We try to mortify ourselves into better habits. We tell ourselves that we’re fat, lazy, out of shape and weak; that our procrastination is holding us back – and it’s all our fault. That negative self-talk doesn’t feel great, but we assume shaming ourselves is the only way to successfully motivate positive changes.

But that approach is surprisingly ineffective, particularly if your goal is to feel happier in the new year. First, our minds have bad intuitions about what we can do to improve our mood. The research shows we make happiness mistakes all the time: we complain too much, thinking we’re letting off steam, but do so at the cost of noticing the good things in life. We avoid social situations, thinking alone time is the cure for our blues, but research shows we’d be happier if we connected with a friend. We also assume that happiness involves changing our circumstances: losing weight, getting buffer and earning more money. But as someone who teaches an entire course on the science of happiness, I know the research shows most of these popular January goals don’t improve our happiness as much as we assume.

That’s why I advise my students to take a more evidence-based approach to picking resolutions, inspired by scientific studies of what does make us feel good. For example, instead of trying to change your body shape this month, focus on changing your mindset. Try counting your blessings before you fall asleep. It sounds cheesy, but research shows that the simple act of writing down three to five things you’re grateful for each day can significantly boost your wellbeing in as little as two weeks. Another positive mindset shift involves becoming more present. Research by Harvard psychologist Dan Gilbert and colleagues shows that no matter what we’re doing, we’re usually happier when we’re paying attention. So why not commit to boosting your presence with a few minutes of meditation every morning? Finally, consider switching from a selfish me-me-me mindset to one that’s a bit more focused on others. Study after study shows that people are happier when they’re helping people in need.

Then there’s the question of how we go about achieving our resolutions; the science suggests tough love is not the most effective way. Research by University of Texas at Austin psychologist Kristen Neff has shown that it’s easier to change for the better if we take the opposite approach, treating ourselves kindly and recognising that suffering and frailty are just part of being human. When that drill sergeant wants to pipe up, switch to a different inner monologue. Talk to yourself like a loving parent or coach who’s trying to soothe rather than scold. Remind yourself that being human means not being perfect all the time, and give yourself compassionate touches: Neff suggests stroking your hand as you would to soothe a friend. While this might seem self-indulgent and hippy-dippy, the science shows it’s an effective way to meet our goals. Neff and others have found that people who are self-compassionate eat better, exercise more and are happier with their bodies. They also procrastinate less and bounce back more resiliently after failures.

By recognising the ways our minds lead us astray, we can be sure not to squander the powerful fresh start effect of the new year. Doing so requires overcoming the overwhelming cultural urge to pursue total change, as well as extending ourselves a little grace. And that’s why I’ve committed to a different resolution this year: instead of hitting the gym or the diet books, I’ve pledged a little more self-compassion. I suggest you do, too.

• Dr Santos’s podcast, The Happiness Lab, has more tips on forming better resolutions this month.