According to St. Gregory the Sinaite there are three degrees in eating: temperance, sufficiency, and satiety. Temperance is when someone wants to eat some more food but abstains, rising from the table still somewhat hungry. Sufficiency is when someone eats what is needed and sufficient for normal nourishment. Satiety is when someone eats more than enough and is more than satisfied. Now if you cannot keep the first two degrees and you proceed to the third, then, at least, do not become a glutton, remembering the words of the lord: 'Woe unto you that are full now, for you shall hunger' (Lk. 6:25). Remember also that rich man who ate in this present life sumptuously every day, but who was deprived of the desired bosom of Abraham in the next life, simply because of this sumptuous eating.
Even if we have thousands of acts of great virtue to our credit, our confidence in being heard must be based on God's mercy and His love for men. Even if we stand at the very summit of virtue, it is by mercy that we shall be saved.
The roof of any house stands upon the foundations and the rest of the structure. The foundations themselves are laid in order to carry the roof. This is both useful and necessary, for the roof cannot stand without the foundations and the foundations are absolutely useless without the roof-- no help to any living creature. In the same way the grace of God is preserved by the practice of the commandments, and the observance of these commandments is laid down like foundations through the gift of God. The grace of the Spirit cannot remain with us without the practice of the commandments, but the practice of the commandments is of no help or advantage to us without the grace of God.
Great is this mystery, and great is the mercy of God towards man. If all the people of the earth knew how deeply the Lord loves man their hearts would be filled with love of Christ and Christ’s humility, and they would seek to be like Him in all things. But man cannot do this by himself, for it is only in the Holy Spirit that he can become like unto Christ. Man that is fallen purifies himself through repentance, and is made new by the grace of the Holy Spirit, and in all things becomes like unto the Lord.
Almsgiving heals the soul's incensive power; fasting withers sensual desire; prayer purifies the intellect and prepares it for contemplation of created beings. For the Lord has given us commandments which correspond to the powers of the soul.
I shall speak first about control of the stomach, the opposite to gluttony, and about how to fast and what and how much to eat. I shall say nothing on my own account, but only what I have received from the Holy Fathers. They have not given us only a single rule for fasting or a single standard and measure for eating, because not everyone has the same strength; age, illness or delicacy of body create differences. But they have given us all a single goal: to avoid over-eating and the filling of our bellies... A clear rule for self-control handed down by the Fathers is this: stop eating while still hungry and do not continue until you are satisfied.
Let us be satisfied simply with what sustains our present life, not with what pampers it. Let us pray to God for this, as we have been taught, so that we may keep our souls unenslaved and absolutely free from domination by any of the visible things loved for the sake of the body. Let us show that we eat for the sake of living, and not be guilty of living for the sake of eating. The first is a sign of intelligence, the second proof of its absence.
An elder prescribes the following rule of conduct for the monastic table: 'When you sit to eat, brother, do not be overcome by the demon of gluttony, which compels you to eat in a disorderly way and in haste and to desire to taste many kinds of food together. Learn to eat modestly and in an orderly way and maintain a measure of restraint.'
If your heart has been softened either by repentance before God or by learning the boundless love of God towards you, do not be proud with those whose hearts are still hard. Remember how long your heart was hard and incorrigible. Seven brothers were ill in one hospital. One recovered from his illness and got up and rushed to serve his other brothers with brotherly love, to speed their recovery. Be like this brother. Consider all men to be your brothers, and sick brothers at that. And if you come to feel that God has given you better health than others, know that it is given through mercy, so in health you may serve your frailer brothers.
If you examine your life well, you will find many instances when God showed His unmistakable mercy to you. Trouble was brewing, but it passed you by for some reason. God delivered you. Acknowledge these and thank God, Who loves you.