How long does it take to form a habit?

In 1960, Dr Maxwell Maltz discovered that it took 21 days for patients to get used to the results of an operation and adjust to new routines.

He wrote: “These, and many other commonly observed phenomena tend to show that it requires a minimum of about 21 days for an old mental image to dissolve and a new one to jell.”

Everyone forgot about “minimum”. When he published his book Psycho-Cybernetics, the 21-day myth was born.

Because it was said often enough, everyone started to believe it.

21 days seems realistic — not too short or too long, and it feels manageable. Everyone wanted to believe that they can become a new person in 21 days, and the myth spread like wildfire.

No matter how much you want to believe it, it does not take 21 days to change. It’s much more complex than that. Some behaviours are more rewarding and easier to build. Think about it — does it really take 21 days to develop a crack habit?

Philippa Lally, a health psychology researcher, found out the answer:

On average, it takes 2 months to form a habit — 66 days, to be exact. It can range from 18 days to 254 days, depending on the person, their behaviour and circumstances. Another interesting finding in the research is that missing a day does not harm the habit-building process.

What does Lally’s research teach us?

  • Building habits is a marathon, not a sprint. Don’t feel pressured if you don’t change overnight.
  • Mistakes during your journey do not have any long term impact. Instead, by learning from your mistakes, you can become better at building habits.

The 21-day myth can lead to frustration — what if going to the gym does not become automatic by Day 22? We should forget about how many days it takes and focus on showing up instead. If you want to get to day 1000, you need to start with Day 1.

In fact, you can start right here and right now. Make your Day 1 today by taking the first action, no matter how small it is — even if it is doing 1 pushup, reading 1 page, or writing 1 sentence.

Originally published at on August 21, 2021.




3rd-year medical student. Check out my blog at

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Haikal Kushahrin

Haikal Kushahrin

3rd-year medical student. Check out my blog at

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