Traditionally, the new or the full moon days are considered to be the rest days within the Ashtanga Yoga community. One might have experienced feeling rajasic, energetic, emotional as the full moon approaches. Or on the opposite side tamasic, sluggish, grounded around the new moon day. Since the moon cycles correlate with ones energetic levels it is advised to restrain from asana practice during these days and restore the balance
Check moon phases for more info on upcoming moon days.