Many functions in our bodies are essential to human life. The heart and temperature regulation are a couple of examples. But one physiological function intimately connects us to life - breathing.

The importance of the breath is described in many ancient texts. Below is a great example from the sanskrit scripture the Brihadaranyaka Upanishad:

The senses when quarrelling together as to who was the best, went to Brahman and said: ‘Who is the richest of us?’ He replied; ‘He by whose departure the body seems worst, he is the richest.’

The tongue (speech) departed, and having been absent for a year, it came back and said: ‘How have you been able to live without me?’

They replied: ‘Like unto to people, not speaking with the tongue, but breathing with the breath, seeing with the eye, hearing with the ear, knowing with the mind, generating with seed. Thus we have lived.’ Then speech entered in.

The eye (sight) departed, and having been absent for a year, it came back and said: ‘How have you been able to live without me?’

They replied: ‘Like blind people not seeing with the eye, but breathing with the breath, speaking with the tongue, hearing with the ear, knowing with the mind, generating with seed. Thus we have lived.’ Then the eye entered in.

The ear (hearing) departed, and having been absent for a year, it came back and said: ‘How have you been able to live without me?’

They replied: ‘Like deaf people not hearing with the ear, but breathing with the breath, speaking with the tongue, seeing with the eye, knowing with the mind, generating with seed. Thus we have lived.’ Then the ear entered in.

The mind departed, and having been absent for a year, it came back and said: ‘How have you been able to live without me?’

They replied: ‘Like fools, not knowing with the mind, but breathing with the breath, speaking with the tongue, seeing with the eye, hearing with the ear, generating with seed. Thus we have lived.’ Then the mind entered in.

The seed departed, and having been absent for a year, it came back and said: ‘How have you been able to live without me?’

They replied: ‘Like impotent people, not generating with seed, but breathing with the breath, speaking with the tongue, seeing with the eye, knowing with the mind. Thus we have lived.’ Then the seed entered in.

The (vital) breath, when on the point of departure, tore up these senses as a great, excellent horse of the Sindhu country might tear up the pegs to which he is tethered. They said to him: ’Sir, do not depart. We shall not be able to live without thee’.

Translation from The Complete Yoga Book by James Hewitt