He is not yet a faithful servant who bases himself on bare knowledge alone; a faithful servant is he who professes his faith by obedience to Christ, Who gave the commandments.
Accordingly, a man will neither be puffed up through pride, nor cast down by despair, if he uses the good things divinely bestowed on him, to the glory of the Giver; withholding his desires from the things which he knows will hurt him. And so he that would preserve himself from the wickedness of envy, from the corruption of sensuality, from the unrest of anger, from the desire of revenge, will be purified by the sanctifying power of true abstinence, and will taste the joy of imperishable delights, so that by making spiritual use of them, he will learn to change earthly possessions into heavenly, not by storing what he has received, but by multiplying more and more that which he has been given.
There is a sin which is always 'unto death' [1 Jn 5:16]; the sin which we have not repented. Even a saint's prayers will not be heard for the unrepented sin. The person who repents correctly does not imagine that his sins are cancelled through his own effort; but knows that through this effort he makes peace with God.
Ye victorious martyrs who endured torments gladly for the sake of the God and Saviour; ye who have boldness of speech towards the Lord Himself; ye saints, intercede for us who are timid and sinful men, full of sloth, that the grace of Christ may come upon us, and enlighten the hearts of all of us that so we may love him.
If we want to do something but cannot, then before God, Who knows our hearts, it is as if we have done it. This is true whether the intended action is good or bad.
Even a pious person is not immune to spiritual sickness if he does not have a wise guide -- either a living person or a spiritual writer. This sickness is called prelest, or spiritual delusion, imagining oneself to be near to God and to the realm of the divine and supernatural. Even zealous ascetics in monasteries are sometimes subject to this delusion, but of course, laymen who are zealous in external struggles (podvigi) undergo it much more frequently. Surpassing their acquaintances in struggles of prayer and fasting, they imagine that they are seers of divine visions, or at least of dreams inspired by grace. In every event of their lives, they see special intentional directions from God or their guardian angel. And then they start imagining that they are God's elect, and often try to foretell the future. The Holy Fathers armed themselves against nothing so fiercely as against this sickness -- prelest.
The right practice of abstinence is needful not only to the mortification of the flesh but also to the purification of the mind. For the mind then only keeps holy and spiritual fast when it rejects the food of error and the poison of falsehood.
If Moses, who was a god to Pharaoh, was shut out from the Land of Promise because of one word, how much more will not the evil speech of our tongue, by which we offend and hurt both God and man, shut us out from heaven?