We have all been there.
You ride a few days in a row, and something is just not clicking. Maybe you are working on something new, learning a correct leg-yield perhaps, or pushing to improve the quality of some existing training, such as demanding more collection at the canter, and it is just not happening. Your horse is frustrated and tense, and so are you. You take a few days off, and the timidly attempt the same problem during your next ride. All the sudden, it just clicks. No more confusion- everything just flows easily, and whatever was blocking you before is now working well.