Following the phases of the moon
Traditionally Ashtanga yoga is not taught on Moon Days (when there is a full moon or a new one). This works well when you have fewer commitments in life and can fit in a 6 day a week practice. In my earlier days of practice, I always observed moon days. Nowadays, with much less free time, I practice when I get the opportunity, even on the full and new moons. I do find it useful, however, to be aware of the phases of the moon and how they affect my energy levels and practice correspondingly.