Breath is vital not only to the body but also to the mind. The mind which is the source of thought and the vital (pranik) energy that is the source of breath are the same. Healthy or unhealthy thoughts are to be attributed to different vibrations of the nadis*. You may test this for youself. See for yourself how you breathe when you are at peace before the sanctum of a deity or in the presence of a great and wise person and how you breathe when your mind is quickened by desire or anger. The happiness you experience when you take part in something divine, like a bhajan or a temple festival, must be different from the pleasure that sensual gratification gives you: the vibrations of the nadis concerned will also be correspondingly different.
(Sri Chandrasekharendra Saraswati Mahaswamiji, Sage of Kanchi)
* Nāḍī ( nerve, blood vessel, pulse) are a term for the channels through which, in traditional Indian medicine and spiritual science, the energies of the physical body, the subtle body and the causal body are said to flow. Within this philosophical framework, the nadis are said to connect at special points of intensity called nadichakras.
'Introduction To Hindu Dharma'
By Jagadguru His Holiness Sri Chandrasekharendra Saraswati Swamigal (Author)
Understand authentic Hinduism directly from one of the most revered Hindu spiritual leaders of the twentieth century. This book consists of selections from the more than 2,000 discourses of Kanchi Sankaracharya. It covers the topics of prayer and virtue, Hindu metaphysical truth and the conflict between traditional Hindu dharma and modernity. A sage in the Shankara tradition, he was one of the most beloved and honoured spiritual figures of the twentieth century in India and much of Asia and Europe. But, despite high praise from the likes of H.R.H. Constantine, King of Greece and Indira Gandhi, former prime minister of India, he is not as well known in the West. This book, therefore, has the distinction of introducing both the sage and his spiritual legacy to the Western world in the form of an irreplaceable introduction to Hinduism in today's world. This book consists of selections from the more than 2,000 discourses of Kanchi Sankaracharya. It covers the topics of prayer and virtue, Hindu metaphysical truth and the conflict between traditional Hindu dharma and modernity.