But countless studies have shown that a cue and a reward, on their own, aren't enough for a new habit to last. Only when your brain starts expecting the reward—craving the endorphins or sense of accomplishment—will it become automatic to lace up your jogging shoes each morning. The cue, in addition to triggering a routine, must also trigger a craving for the reward to come.
The Power of Habit: Why We Do What We Do in Life and Business (ed. Random House, 2012) - ISBN: 9780679603856