Gluttony makes a man gloomy and fearful, but fasting makes him joyful and courageous.
And, as gluttony calls forth greater and greater gluttony, so fasting stimulates greater and greater endurance.
When a man realizes the grace that comes through fasting, he desires to fast more and more.
And the graces that come through fasting are countless....
Saint Nikolai of Zicha
The desire for good food is a trap of the evil one. Whoever does not get rid of this desire is caught by the enemy’s hook and is fried in his own fat by his burning flesh. On the contrary, the desire for spiritual nourishment takes the heart away from earthly things and raises the soul to Heaven, where it tastes the food of angels.
St. Paisios
The beginning of a fruit is a blossom, while the beginning of a productive life is self-restraint. A sufficient quantity of matter will fill a container, but a stomach, even if it bursts, will not say: enough. A body sparsely fed is like a well-ridden horse — it will never throw its rider. Just as a dead enemy will not evoke fear, so a body mortified through fasting will not disturb your soul.
(St. Nilus of Sinai)