Why take rest on Moon Days?

Traditionally Ashtanga yoga is six day a week practice, with rest days taken once a week, as well as on a full moon and a new moon (moon days). Why don't we practice on these days?

Here are a selection of quotes from Guruji, Sharath and other senior teachers to help answer this question.

Guruji, France, 1991

"That day is very difficult day. Two stars one place (conjunction) is going. New moon also, full moon also. That day very dangerous day. You (take) practice (on that day), anyone can have a small pain starting. That pain is not going very quickly. Long time he is taking. Some broken possible. That is why that day don’t do".  source

Tim Miller, Ashtanga Yoga Centre

Like all things of a watery nature (human beings are about 70% water), we are affected by the phases of the moon. The phases of the moon are determined by the moon’s relative position to the sun. Full moons occur when they are in opposition and new moons when they are in conjunction. Both sun and moon exert a gravitational pull on the earth. Their relative positions create different energetic experiences that can be compared to the breath cycle. The full moon energy corresponds to the end of inhalation when the force of prana is greatest. This is an expansive, upward moving force that makes us feel energetic and emotional, but not well grounded. The Upanishads state that the main prana lives in the head. During the full moon we tend to be more headstrong.

The new moon energy corresponds to the end of exhalation when the force of apana is greatest. Apana is a contracting, downward moving force that makes us feel calm and grounded, but dense and disinclined towards physical exertion.

The Farmers Almanac recommends planting seeds at the new moon when the rooting force is strongest and transplanting at the full moon when the flowering force is strongest. Practicing Ashtanga Yoga over time makes us more attuned to natural cycles. Observing moon days is one way to recognize and honor the rhythms of nature so we can live in greater harmony with it. source

Sharath Jois, Mysore, December 2015

"[The position of the stars and planets] affects our minds also.  Sometimes many bad things will happen to you for a few years. Call it Saraswathi. We are all dependent on the moon, stars, planets. When these things come [moon days] the mind goes very active. More energy on these moon days. These energies might hurt your body or mentally when you are doing asana. Don't make your mind too active. Just rest. In the old days people would not travel on moon days. You might damage or hurt yourself

Richard Freeman, Yoga Workshop

"It’s part of the traditional approach to take time off during the new and full moons. This is partly due to the Indian astrological belief that it is not auspicious to do certain things on moon days. Because we are part of this lineage, we have chosen to honor the moon days in this way.

In addition, once you practice on a daily basis (six days a week is recommended), you’ll notice that being invited to take a day off is a luxury. The body can rest (after all the ashtanga practice is physically demanding) and on moon days you feel like you have a huge chunk of unspoken for “free time” when you’re used to daily practice" 

Click here for this year's moon day calendar