The mind-blowing reason why your resolutions fail

For over a decade, all my New Years’ resolutions followed a depressingly predictable pattern. 

Every January 1st I poured away the last of the Christmas booze, laced up my running shoes and dusted off the spiraliser.

Yet, within a few short weeks I was pounding the merlot in my unicorn onesie, eating spaghetti that was definitely not made of spiralised courgette.

But, when it comes to failed resolutions, I’m definitely not alone. In fact, the vast majority of resolutions barely make it to mid-January. It’s a phenomenon so ubiquitous that there’s even a name for it: Quitter’s Day.1 This year, Quitter’s Day falls on January 17th (I’m surprised Clintons doesn’t sell a card for it yet).2 So, if your mate Smug Simon is boasting about his new wholefood vegan lifestyle, chances are he will have face-planted into a doner kebab by Sunday. 

I used to think failed resolutions were purely down to a lack of willpower. But with around 80% of people failing to meet their New Year’s goals,3 could there be more to it than that? To find out, let’s delve into a little cognitive psychology…

The brain dichotomy

Our brains are incredible computing machines. Yet, much like your laptop, they are prone to bugs and processing errors. Brain boffin and Nobel Prize winner Daniel Kahneman explored such grey matter glitches in his best-selling book, Thinking, Fast and Slow.4 The central thesis of Kahneman’s work is that there are two different ways the brain forms thoughts: System 1 and System 2.

While System 1 thinking is quick, automatic, and expends little effort, System 2 thinking is slow, infrequent and effortful. In fact, System 2 thinking requires so much effort that it causes you to miss things happening before your very eyes (watch this video to see what I mean). Yet, speedy, sensitive System 1 thinking isn’t without its faults. Much like a typical BMW driver, it cuts corners, makes irrational manoeuvres and never checks its blind spots. When System 1 thinking takes hold of the cognitive steering wheel, it can result in a dizzying array of irrational biases that affect our decision-making. 

The resolution saboteur

So, what has all this got to do with resolutions? Cognitive biases affect our ability to think rationally and act upon the facts before us. They’re the reason you’re more likely to reach for the takeaway menu after a mentally tiring day at work, even if you know it will make you feel lousy tomorrow. Here are just some of the ways your brilliant brain can lead you astray, despite your best intentions:

Optimism bias

I used to launch into my New Year’s resolutions with the zeal of an untrained border collie. “This is the year I finally kick my Kinder Bueno habit and become a shining beacon of zen and poise”, I would say to myself every single year. I didn’t plan for failure, because failure didn’t exist in my perfectionist fantasies.  

While unrelenting optimism may sound like a good thing, Kahneman describes this so-called ‘optimism bias’ as “the most significant of the cognitive biases”, as it creates a tendency for us to overestimate our ability to control events. This is why when we face obstacles that stand in the way of our good intentions (like the time my bullet blender exploded and liquified kale went everywhere), we’re far more likely to throw in the towel and fall back on bad habits.

The sunk cost fallacy

Picture the scenario. You’ve broken up with sugar and stocked up on vegetables. For a few days everything is alright. You are excited to start a new life with your latest squeeze, stevia. But soon your resolve begins to weaken. Life without sugar just isn’t so, well, sweet. One day while grazing your cupboards you spot it: half a packet of Oreos. It would be a shame to just throw them away, right? Those crumbly circles of joy barely touch the sides as they go down the hatch. So long, stevia.

This is an example of what is known as the ‘sunk cost fallacy’, which is our tendency to avoid abandoning something we have made an investment in. You could throw the Oreos away, but your loss-adverse brain considers it a waste; even if you know logically that you have more to gain in the future by eschewing the Oreos for more healthful choices. 

The anchoring effect

When you sit down for a meal, you listen to your hunger/fullness cues and stop eating when you’re satiated. Right? Well actually, research shows that for many of us, portion size serves as an influential factor in determining how much to eat. In a fascinating experiment,5 participants were asked to imagine they were in a restaurant and about to be served a bowl of pasta (mmm… pasta). One group was asked “will you eat more or less than 75g of pasta?”, while another group was asked “will you eat more or less than 300g of pasta?”. Both groups were then asked to estimate how many grams of pasta they thought they would eat. A third (control) group was just asked the second question. The result? Participants who imagined larger portions estimated they would eat significantly more food than the third group, while the opposite effect was seen among those who imagined smaller portions.

This is an example of a phenomenon known as the ‘anchoring effect.’ By ‘anchoring’ to high or low numbers, researchers could influence how much penne their pasta-loving participants thought they could put away. Something to think about next time you order from Zizzi. 

Are we wired to fail?

Okay, so now we know a little more about our brilliant brains (and their tendency to be blindingly stupid): does this mean failure is inevitable? Fortunately, it’s not all doom and gloom. According to a recent article,6 “guided reflection and cognitive forcing strategies deflect bias through close examination of our own thinking processes.” In other words, simply being aware of our biases can help us to overcome them.

So, the next time you find yourself unconsciously reaching for the Häagen-Dazs, take a deep breath and tap into your slothful System 2 thinking. You might just make it past Quitter’s Day.  


  1. The Independent. What is Quitter’s Day and when does it take place? Available at: Accessed January 2021.
  2. January 17th: Ditch New Year’s Resolution Day. Available at: Accessed January 2021. 
  3. Why 80 percent of New Year’s resolutions fail. Available at: Accessed January 2021.
  4. Kahneman, Daniel. Thinking, Fast and Slow. Farrar, Straus and Giroux. 2011.
  5. Marchiori D, et al. Appetite. 2014;81:108–115.
  6. Doherty TS and Carroll AE. AMA Journal of Ethics. 2020;22(9):E773–E778.