“A hesychast is one who tries to enshrine what is bodiless within his body.”…Do you see how St John [Klimakos] has shown, not simply from the spiritual but even from a human point of view, how vital it is for those who seek to be true masters of themselves, and to be monks according to their inner self, to install or possess the intellect within the body?
Nor is it out of place to teach beginners in particular to look within themselves and to bring their intellect within themselves by means of their breathing….Since the intellect of those recently embarked on the spiritual path continually darts away again as soon as it has been concentrated, they must continually bring it back once more; for in their inexperience they are unaware that of all things it is the most difficult to observe and the most mobile. That is why some teachers recommend them to pay attention to the exhalation and inhalation of their breath, and to restrain it a little, so that while they are watching it the intellect too may be held in check.
This they should do until they advance with God’s help to a higher stage and are able to prevent their intellect from going out to external things, to keep it uncompounded, and to gather it into what St Dionysios calls a state of “unified concentration”.
This control of the breathing may, indeed, be regarded as a spontaneous consequence of paying attention to the intellect; for the breath is always quietly inhaled and exhaled at moments of intense concentration, especially in the case of those who practice stillness both bodily and mentally.
Such people keep the Sabbath in a spiritual fashion and, so far as is possible, they rest from all personal activities; they strip their soul’s powers free from every transient, fleeting and compound form of knowledge, from every type of sense-perception and, in general, from every bodily act that is under our sway, and so far as they can, even from those not entirely under our sway, such as breathing.
~St Gregory Palamas (Philokalia vol.4, pp.336-337)