Making It Stick: Turning a Reset Into a Winter Habit
Sixty-six days.
That was the median time it took volunteers in a well-known study from University College London to make a new daily behavior feel automatic. The researchers, led by health psychologist Phillippa Lally, asked 96 people to choose one small habit, like drinking a glass of water with lunch or going for a short run before dinner, and to track it every day. For some people it clicked in 18 days. For others it took an estimated 254.
If you started a cold plunge or sauna routine as the weather turned, 66 days from early October lands in the first week of December. Holiday schedules tend to get unpredictable right around then, and knowing the timeline ahead of time helps.
Where the 21-day idea came from
Many of us grew up hearing that it takes 21 days to form a habit. Psychology Today's overview of habit formation calls that figure a pop psychology refrain and notes that the real timeline depends on many factors, including the behavior, the person, and the setting.
The Lally study adds a reassuring detail. Missing a single day didn't meaningfully set people back. What mattered was coming back to it. So if you miss a plunge in the second week, you haven't lost your progress.
What turns a reset into a habit
Psychology Today describes habits as a loop with three parts: a cue, a routine, and a reward. Repeating a behavior in the same context strengthens the brain pathways behind it until the behavior starts to run on its own. Rewards help too, likely because they trigger dopamine, which plays a central part in how habits form.
Cold and heat are unusual in that the reward comes built in. Most people feel noticeably more alert after a cold plunge and more relaxed after a sauna. The trick is to actually notice it. After a session, take a few seconds to register how you feel. Some people keep a two-line note on their phone with the date and one word for their mood. Over a few weeks, that record becomes its own reason to keep going.
The context matters just as much. Plunging at the same time, in the same order, after the same trigger gives your brain a clean pattern to learn. Changing things every day makes the loop harder to form.
The payoff that takes decades
It's easy to lose sight of why any of this matters when you're standing next to cold water on a dark morning. A large Harvard study helps put it in perspective.
As Harvard Health reported, researchers followed about 111,000 people for more than 30 years. They looked at five habits: not smoking, limiting alcohol, eating a healthy diet, keeping a healthy weight, and exercising at least 30 minutes a day. People who kept four or five of them at age 50 gained up to about a decade of life free from major chronic diseases like cancer, heart disease, and type 2 diabetes, compared with people who kept none.
Cold plunging and sauna aren't on that list. We think they still belong in the conversation, because a routine you enjoy tends to pull other routines along with it. A morning plunge often comes with getting outside early, moving your body, and going to bed at a steadier time. Our post on the 7 pillars of vibrant energy covers how those pieces fit together, from morning sunlight to a consistent sleep schedule.
Size it for winter
The biggest mistake with a new routine is building it around your best week. Winter will hand you plenty of weeks that aren't your best. It helps to decide on three versions ahead of time and let yourself move between them.
| Cold plunge | Sauna | |
|---|---|---|
| Minimum (a hard week) | Two plunges, 1 minute, 55 to 60°F | One session, 10 minutes |
| Standard (a normal week) | Three or four plunges, 2 to 3 minutes, 50 to 59°F | Two or three sessions, 12 to 15 minutes, 165 to 175°F |
| Full (a good week) | Most days, up to 5 minutes, at a temperature you've built up to | Three or four sessions, up to 20 minutes total, with a cold plunge between rounds if you enjoy contrast |
These ranges are starting points. Adjust them to how you feel during and after each session, and move down a tier any time sleep, illness, or stress calls for it. A minimum week still counts as doing the habit.
Safety
Cold and heat both place real demands on your heart and blood pressure. If you have a heart condition, high blood pressure, diabetes, or are pregnant, talk to your doctor before starting. Skip both when you're sick or after drinking alcohol, stay hydrated around sauna sessions, and get out of cold water if you feel numb, dizzy, or can't slow your breathing.
Where to start this week
Pick your minimum version and write it down. Choose one cue that will be there every day, like your alarm, your first coffee, or getting home from work, and attach the routine to it. Then give it time. If the research is any guide, it may take until December or later before this feels automatic, and that's normal.
Sources
- Harvard Health Publishing, "Healthy habits mean more disease-free years" (January 8, 2020)
- Psychology Today, "Habit Formation"
- Plunge, "The 7 Pillars of Vibrant Energy"
- Lally et al., "How are habits formed: Modelling habit formation in the real world," European Journal of Social Psychology, 2010
- Li et al., "Impact of healthy lifestyle factors on life expectancies in the US population," The BMJ, 2020
