Lots of people say it takes 21-days.
The reality is it depends entirely on how much action you take! Forming habits comes down to the frequency of action, not the passage of time.
So if you spend 21 days thinking, learning and planning a change in your life, there might be some benefits to be had, but realistically you’ve spent three weeks procrastinating.
Change comes from action…ideally really simple, easy to repeat actions. If it only takes 5 mins and it’s really easy to do you’re much more likely to do it, to feel good and to do it again, and again, until it becomes part of your routine. And ultimately something you do without thinking.
So stop trying to find the perfect way to fit exercise / good nutrition / [insert your goal here] and actually do what you’re striving for – get after it and get those reps in!