It’s a natural human urge to want good things and to want them NOW. So, the question I hear most often when someone is considering change is "How long will it take?" When it comes to habits, plenty of research studies have aimed to quantify this. Answers vary from 18 to 254 days, with an average of 66 days for behaviour to become automatic.
The oft-quoted "21 day" myth references a situational observation made by Dr Maxwell Maltz in his book "Psycho-Cybernetics". He actually 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 gel.” Written in the 1960s, the book became popular and over the years his personal experience somehow morphed into a commonly accepted fact!
Everyone wants to know the secret to reducing 254 days to 18. One answer is to speed up the rate of repetition on your newly selected habit. Why? Because the mechanism for a habit to embed in your unconscious is based on repetition, or rote learning. The process is further accelerated if your chosen habit is pleasure-based. Enjoyable behaviour prompts your brain to release dopamine, which creates a craving and thereby sets up a looping pattern.
In short, make your new habit fun, then do it over and over....so it sticks!