Some people say it takes 21-days for a new habit to stick. Some say it takes 66-days for a new habit to stick. Currently, I am struggling with getting good habits started (which is another story for another time).
If you think 21-day rule or even 66 is too daunting... here's a guy that says never take more than 2 days off of a workout.
Check out his video to see if this could work for you.