If you do not cut off the inner flow of evil thoughts by means of prayer and humility, but fight against them merely with the weapons of fasting and bodily hardship, you will labor in vain. But if through prayer and humility you sanctify the root, as we said, you will attain outward sanctity as well. This it seems to me is what St Paul counsels when he exhorts us to gird our loins with truth (cf. Ephesians 6:14).
One of the fathers has excellently interpreted this as signifying that when the contemplative faculty of the soul tightly girds the appetitive faculty it also girds the passions manifested through the loins and genitals. The body, nevertheless, is in need of hardship and moderate abstention from food, lest it become unruly and more powerful than the intelligence. Thus all the passions of the flesh are healed solely by bodily hardship and prayer issuing from a humble heart, which indeed is the poverty in spirit that the Lord called blessed.
~St Gregory Palamas (Philokalia vol.4, p.310)