"According to yoga teachings ², it takes:
40 days to change a bad habit into a positive one;
90 days confirms the new habit in you;
120 days allows the new habit to become who you are;
1,000 days ensures you have mastered the habit."
"you’re focused and consistent. This is a round number and will vary from person to person and habit to habit. Often you’ll read a magical “21 days” to change a habit, but this is a myth with no evidence. Seriously — try to find the evidence from a scientific study for this. A more recent study shows that 66 days is a better number (read more). But 30 days is a good number to get you started. Your challenge: stick with a habit every day for 30 days, and post your daily progress updates to a forum."