66 days. About 2 months - that's how long it takes for a new behavior to become a habit . . . that is, something that's automatic. So says a University college of London study. Make it easier on yourself by picking a set time each day to practice your habit - whatever time you think it'll be the easiest for you to stick with and tolerate.
So what's it going to be? A big salad for lunch? Making a shopping list/meal plan every weekend? A new exercise plan? The last time I did this in earnest was when I was 20 and learning how to exercise for the first time. I capitalized on my trait as a morning person by getting up at 6:00 every morning and going for a walk/run . . . which turned into a run . . . which turned into a years-long jogging habit and a 40-pound weight loss.
If you start now, you'll have a new habit firmly in place by the time the weather turns! What're you gonna do?