In yoga we are encouraged to reflect on the changing nature of life. We practice the Yamas, the restraints of proper conduct, Aparigraha, non-attachment, and Satya, truthfulness, by accepting that the things we love are going to change. We practice not clinging to what is, because we know it will change, we will change. 

In the Upajjhatthana Sutta  the Buddha reflected upon what he called the Five Remembrances. He reminded us that we cannot escape old age, we cannot escape illness, we cannot escape loss, and we cannot escape death. The only thing we can control is our actions, our thoughts and deeds. It can be seen as very heavy stuff, but is a clarion call to live fully because nothing lasts.

Then along comes the Bṛhadāraṇyaka Upaniṣad, it takes all of this and, doesn’t dismiss it, but tells us that in the midst of unrelenting change we are always whole.   

पूर्णमदः पूर्णमिदं पूर्णात्पूर्णमुदच्यते ।
पूर्णस्य पूर्णमादाय पूर्णमेवावशिष्यते ॥

The Pūrṇam Mantra arises out of this teaching of the Bṛhadāraṇyaka Upaniṣad and is one of what are collectively known as the Shanti Mantras, or Peace Mantras. Mantra like these are chanted before and after the study and discourse, plus at other times, to calm and focus the mind. The Pūrṇam Mantra is chanted before reading the Bṛhadāraṇyaka Upaniṣad and the Isha Upanisad.

Translation: The version I learned during my training in Integrated Movement Therapy (IMT) is my favorite. Stephanie Sisson is the translator, she helped create IMT with Molly Kenny. 

This is whole.
That is whole.
When you take whole from whole
That which remains is whole.
Om. Peace, peace, peace.

Using the Mantra 

Chanting is not only an excellent tool for improving the strength and capacity of our lungs, it also brings focus and calm to an agitated mind. Further, it is a reminder, again and again, that in the midst of change you are still whole.

You can chant it multiple times, closing with the final line on your last chant through.

Sanskrit Mantra in the Latin alphabet (“English”): 

Pūrṇamadaḥ pūrṇamidam
pūrṇāt pūrṇamudacyate
pūrṇasya pūrṇamādāya
oṃ śāntiḥ śāntiḥ śāntiḥ

Mantra with phonetic pronunciation:

poornam-adah poornam-i-dahm
poorn-aat poornam-uda-chya-te
poor-na-sya poornam-ah-da-ya
poornam-evaa va-shi-shya-te
Om shaantih shaantih shaantih-i