Rest is the most important component to showcasing a healthy set of abs. Studies have shown that 8 or more hours of sleep per day helps in the growth of muscles beyond the ages in which humans start to lose muscle mass.
Abs are also very easy to overwork. For most men, and now more women, a healthy set of abs is the marker of virility and healthiness. Becuase of this, many people will concentrate on their abs routine everyday rather than giving your body time to rest.
As a rule of thumb, never concentrate, specifically, on your abs more than 3-4 times a week. There are plenty of other ways to hit your abs indirectly such as kickboxing, sprinting, swimming, Yoga, and stretching.