By serving the senses, the heart is turned away from delight in God; for our inward thoughts, they say, are bound by their perception to the sensory organs that serve them.
Doubting hesitation of the heart introduces cowardice into the soul, but faith can make firm her volition even in the cutting off of the body’s limbs. In the measure that love for the flesh prevails in you, you can never become brave and dauntless, on account of the host of adversaries that constantly surround the object of your love.

St Isaac the Syrian, Homily 1