When you're just beginning a new training/exercise program, you might want to follow the '2 days on, 1 day off' method for a while - after exercising two days, take one day off. Once your body gets used to the exercises, you should increase the difficulty and repetitions or duration, but don't overdo it. Then it would be more like 2 steps forward, 1 step back - or even 3 steps back if you tear, pull, or injure a tissue, ligament, muscle, or bone.