Step three: Maintaining the habit
Most habits are metastable. That means that they can endure for a long time, but if something pushes them out of balance they will fall back to an easier behavior. Exercise is an example of a metastable habit because it requires time and energy even if it is automatic for you.
A good rule of thumb is that the commitment should be equal in time to the loss of habit. So if you’ve stopped exercising for a week, you should commit to following your habit for at least a week to get back to an equilibrium. If you’ve stopped for more than two months on a daily habit, you should probably treat it like conditioning a new habit.