When I was in college, I had a Health professor tell me that he used to like salt and then had to quit for his blood pressure. He quit it for three weeks and afterwards didn’t mind the unsalted taste and even couldn’t add salt anymore because he could taste it and didn’t really need it. He then said that if you wanted a habit to stick, you can generally keep it if you just hold out for three weeks. Now, I didn’t know if there was any scientific basis to that claim, but the point stuck with me: how long did you have to hold out for something, and what is going on?
I am not the only one who asked that question. A great article from howstuffworks.com did some research and found that other than some mentioning in self-help books based on anecdotal and empirical evidence, there wasn’t clinical evidence of this being statistically true for most people. My own research, however, found an interesting article that tested how long it took for something to become automatic behavior and saw that the time to become automatic behavior ranged from 18 to 254 days. Now, that data cannot be extrapolated to everything because it was focused on a specific behavior done at a specific time and not the same as, say, getting over an addiction or time-consuming activities like exercise, reading, or practicing an instrument. But it did find the habit start to kick in around that three-week window and saw huge improvements within that range, which is interesting.
So what does that mean for you in your life, and why did I call this “you can get used to anything in three weeks” instead of focusing specifically on habit forming? Well, there’s a combined point here: this is about habits and improvement and adaptation. In your life, you want to both form good habits and be able to adapt to change both good and bad in your life. And the three-week rule, while not a complete scientific inevitability, is such a good bar to help you with both.
Let’s start with habit-forming. If you feel like you have to start doing something for the rest of your life, it can feel daunting. Even a month can feel extreme. While just a week or two doesn’t feel like enough time for something to stick (if you do something weekly, that’s only two instances!). So three weeks is a nice range, and it even allows you to do a three weeks on/one week off combo for certain habits or activities (the research linked above said that missing one instance did not affect habit formation significantly). So it’s more about optimizing the length of time you can hold out without either being overwhelmed or too short to stick. The habit side is especially important, as you need enough repetitions of avoiding a bad habit to let the new habit overtake it, and you need enough new habit instances for your muscle memory to kick in.
Now, what about this “get used to anything” part? Well, this is kind of a point popular with Stoics and Buddhists, but one of two things will be true: a good or bad event will pass, or you’ll get used to it. So, if you have a bad event occur like a loss of money, you will earn it back over time and the sting will go away. Same with relationships coming and going or a bad day at work or in school. But even if something permanently happens, you’ll get used to it. The famous study on adaptation that is famously called “the hedonic treadmill” showed that any event—even traumas such as loss of spouse, parents, children, or bodily functions—can be overcome in about a year where you return to your base level of happiness. But, like anything in life, you typically see greater gains earlier on and it trails off over time. Again, that initial 3-4 weeks is key to push through to adjust to the change.
And that’s the key to that time period: you’re trying to make this your new way of being. Unfortunately, good things are easy to get used to, so even if you hit the lottery you’ll be “over it” (so to speak) within a few weeks as you now act as if this is the “new normal” for you. Bad things are more difficult, but you will find yourself forming new habits and making this new reality your baseline assumption as you go about your day. Three weeks is long enough for the high to wear off and for the low to feel normal despite likely still hurting. Three weeks is long enough for your body to start to default to a new way of behaving and let the old way begin to atrophy and go extinct. It’s long enough for you to feel like this is your new life. Most importantly, it’s long enough for you to begin to identify with this new way of being.
Now, this is not a magic formula. The best example is the New Year’s Resolution, of which most research finds that people have a huge drop-off on January 12, which seems to support the idea that you have to commit to at least three weeks to make it over the habit formation hump. Basically, if you can make it until February 1st, you’re better off than the 64% who quit within the first month. But another 30% will fail within two years according to that data, so it’s not perfect. But the truth is, nothing is perfect. There could be a million reasons why you don’t stick to a new habit or don’t adapt as well as you could to something. And that’s okay. It’s not about the three weeks itself; its about exerting the discipline necessary for that time period so that you can hold out when you need to until it gets easier to accept every day as the new you.
As a final point, don’t forget that there is a lot to “identifying” as a person who has that habit. This is famous in the book, Atomic Habits, by James Clear, who talks about how when you identify as a person who is the kind of person you want to be who has that habit, it helps to reinforce it. Insert your own “CrossFit” joke here about fans talking about it incessantly and making it a lifestyle, but it does help to be the kind of person who does the habit rather than the person who doesn’t normally do it but drags themselves to try it for 12 days per year starting on January 1st.
So if you hit a hard point in your life or want to make a change, don’t dread a lifetime of that new life feeling like you do on day 1. Instead, tell yourself you just need to do this for three weeks, and then when those three weeks pass it’ll be that much easier to stick with it and harder to go back because you have now lived as this new person long enough to feel like it’s more like who you are now than the “old you” that is now in the past. Who knows? Maybe you’ll like the new you and find new, wonderful ways to enjoy your life going forward.