A man that lives on pork, fine-flour bread, rich pies and cakes, and condiments, drinks tea and coffee, and uses tobacco, might as well try to fly as to be chaste in thought.
The principle is this: We must not allow anything into our life that feeds our point of weakness. A soldier doesn't dance through a mind field any more than we should play with a hand grenade. When the enemy's entry points are boarded up, it frees us to hear clearly the voice of our Commander.