Why New Habits Are Hard

Every January, millions of people promise themselves that this year will be different. They are going to start running, stop eating sugar or learn a language. By February, most of them have given up. It is tempting to blame a lack of willpower, but researchers who study habits suggest that the real problem is that we misunderstand how habits work.

A habit is a behavior that has become more or less automatic. You do not decide to brush your teeth every night; you simply find yourself doing it. That is the whole point of a habit: it saves the brain the effort of making the same decision again and again. Psychologists often describe the process as a loop with three parts. First there is a cue, something that triggers the behavior, such as a time of day, a place or a feeling. Then comes the routine, the behavior itself. Finally there is a reward, which makes the brain more likely to repeat the loop next time.

Imagine someone who always has a cookie with their afternoon coffee. The cue might be the three o'clock tiredness, the routine is walking to the kitchen, and the reward is a moment of sweetness and a short break from work. After a few hundred repetitions, the person no longer thinks about it at all. They are used to doing it, and stopping feels strangely uncomfortable.

So how long does it take to form a new habit? You may have heard that it takes twenty-one days. This number is often traced back to a book published in the 1960s, in which a surgeon observed that his patients seemed to need at least three weeks to get used to changes in their appearance. Over time, "at least three weeks" became "exactly twenty-one days", and the idea spread everywhere.

The reality seems to be less convenient. In a well-known study carried out at University College London, volunteers chose a simple new behavior, such as drinking a glass of water after breakfast, and reported every day how automatic it felt. On average, it took around sixty-six days for the behavior to reach its most automatic level, and the range was enormous: from under three weeks for some people to more than eight months for others. Encouragingly, missing a single day did not seem to make much difference.

What does this mean in practice? First, it helps to attach the new habit to an existing cue. If you want to start stretching, try doing it immediately after making your morning coffee, rather than "at some point during the day". Second, make the new behavior as easy as possible to begin with. Promising to read one page is far more realistic than promising to read for an hour, and once you have started, you will often carry on.

Breaking a bad habit follows the same logic in reverse. Instead of relying on willpower alone, try to avoid the cue or make the routine more difficult. People who want to stop checking their phones in bed, for example, often succeed by leaving the phone in another room. It is also worth replacing the old routine with a new one that offers a similar reward, because simply stopping tends to leave a gap that the old habit quickly fills again.

None of this makes change effortless. But it does suggest that failing in February is not a sign of weakness. It is simply a sign that the new habit needed more time, a clearer cue and a smaller first step.