Pope Shenouda III
Fasting Accompanies Self-control
It is commendable that you control yourself against every wrong desire whether it comes to you from your inside or from warring devils, for “he who rules his spirit” is better than “he who takes a city.” (Prov 16:32).
Therefore, hold the reins of self-control in your hand.
In a bodily fast, your body longs for food. You say: No, and you succeed in applying this "No". Make therefore, this willpower include every thought, every wicked desire, every wrong behaviour, and every bodily lust.
As for the person who only controls his food and is controlled by his lusts, his fast is a bodily one. He who cannot control his bodily fast is consequently unable to control himself from bad thought, lusts, and conduct.
Control of your lusts is proof of your asceticism and love of God.