If a person swallows too much food, he is inviting impure thoughts. If he mortifies the stomach, he is creating pure thoughts. Often a lion if it is caressed becomes domesticated, whereas the more you coddle the body, the more it goes wild.
The person who truly comes to serve God must prepare his soul, as it says in the Wisdom of Sirach (2:1), for temptations. Thus, that he will never be surprised or disturbed by what happens, believing that nothing happens without the providence of God and where there is the providence of God certainly what happens is good and for the benefit of the soul. For, everything that God does, He does for our benefit and because He loves us and has pity on us. We must, as the Apostle says, 'In everything give thanks' (1 Thess. 5:18), for His goodness.
Temptations are sent for improvement when God delivers his righteous ones to various temptations, humiliating them for some slight and unimportant offense, or to increase their purity, in order that every uncleanliness of thought, or... dross which He sees they have harbored in secret, may be burnt away in this present life, and that so He may bring them, as it were pure gold, to the future judgment...
Waves of temptation of every sort were aimed at the righteous ones, but they did not grow faint. Glory did not make them haughty, nor did abusive treatment cause them to be despondent. They were always the same; never did the fragrance of their virtues falter.
The belly when filled with all kinds of food gives birth to seeds of wantonness, nor can the mind, when choked with the weight of food, keep the guidance and government of the thoughts. For not only is drunkenness with wine wont to intoxicate the mind, but excess of all kinds of food makes it weak and uncertain, and robs it of all its power of pure and clear contemplation. The cause of the overthrow and wantonness of Sodom was not drunkenness through wine, but fullness of bread. Hear the Lord rebuking Jerusalem through the prophet. 'For how did thy sister Sodom sin, except in that she ate her bread in fullness and abundance?' (Ezek. xvi. 49)
A human being who does not endure courageously the unpleasant burdens of temptations, will never produce fruit worthy of the divine wine-press and eternal harvest, not even if one possesses all other virtues. For one is only perfected through zealously enduring both all the voluntary and involuntary afflictions.
The Lord ordereth 'all things in measure and weight,' and brings on us the temptations which do not exceed our power to endure them, but tests all that fight in the cause of true religion by affliction, not suffering them to be tempted above that they are able to bear.
Without temptations, pure souls are not known, virtue does not show, patience is not discernible. Without temptations, it is impossible for the soul to become healthy. They are the cleansing fire which makes the soul pure and bright.
Whenever in your path you find unchanging peace, beware: you are very far from the divine paths trodden by the weary feet of the saints. For as long as you are journeying in the way to the city of the Kingdom and are drawing near the city of God, this will be a sign for you: the strength of the temptations that you encounter. And the nearer you draw close and progress, the more temptations will multiply against you.