Aristotle says: your repeated actions make up who you are; becoming excellent is forming those positive habits.
Forming new habits can be a huge challenge. Though it’s long been accepted that forming a habit takes about 21 days, more recent research puts that number at or over 66. I don’t think there is a definitive number of days. It probably depends on many variables which a researcher cannot control. Aristotle says, “We are what we repeatedly do. Excellence, then, is not an act, but a habit.” Repetition is what makes a habit stick.
One thing that I think really sets up habit forming for success is always picturing in your mind the habit you want to develop. Essentially, this means looking at the positive rather than the negative; for example, anyone trying to quit smoking who thinks, “I won’t smoke a cigarette today,” has made themselves think about having a cigarette. Here is how that works. Your mind thinks in pictures and your mind can’t see a negative. In the example above, your mind sees “smoke a cigarette” and it can’t visualize “won’t.” This is like a trap because it puts the focus exactly where they don’t want it. But if, instead, the person thinks, “Today I will only fill my lungs with clean, fresh air,” they’re focusing on the positive aspect of the same goal. They see themselves inhaling air in some place where it is clean and fresh.
Forming good habits is something that can heavily contribute to someone’s overall success in life. In the same way, negative habits can lead to a life of illnesses, frustration and unachieved goals. Habits such as eating well, exercising regularly, and getting enough sleep make a huge positive difference. Sets of positive habits lead to a positive lifestyle. You want to incorporate those positive habits into your everyday activities. For example, eating healthy food is not something you do until you get thinner and then go back to the old diet that got you overweight in the first place. It is eating healthy food every day with maybe a splurge once in a while.
For reference: http://www.huffingtonpost.com/james-clear/forming-newhabits_b_5104807.html