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.
Our life and our death is with our neighbor. If we gain our brother, we have gained God, but if we scandalize our brother, we have sinned against Christ.
The man who does not humble himself and does not cleanse his heart from evil desires fasts in vain. He may eat nothing at all, but it will be to no avail if there is evil inside him. He must first cleanse himself from the evil within in order to receive the Lord.
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.
My son, says Scripture, if you come to serve the Lord, prepare your soul for trial, set you heart straight, and patiently endure (Eccles. 2:1-2). And elsewhere it is said: Accept everything that comes as good, knowing that nothing occurs without God willing it. Thus the soul that wishes to do God's will must strive above all to acquire patient endurance and hope. For one of the tricks of the devil is to make us listless at times of affliction, so that we give up our hope in the Lord. God never allows a soul that hopes in Him to be so oppressed by trials that it is put to utter confusion. As St. Paul writes: God is to be trusted not to let us be tried beyond our strength, but with the trial He will provide a way out, so that we are able to bear it (I Cor. 10:13). The devil harasses the soul not as much as he wants but as much as God allows him to. Men know what burden may be placed on a mule, what on a donkey, and what on a camel, and load each beast accordingly; and the potter knows how long he must leave the pots in the fire, so that they are not cracked by staying in it too long or rendered useless by being taken out of it before they are properly fired. If human understanding extends this far, must not God be much more aware, infinitely more aware, of the degree of trial it is right to impose on each soul, so that it become tried and true, fit for the kingdom of heaven?
For as merchants on a voyage, though they find a wind to suit them and the sea calm, but have not yet reached the haven, are always subject to fear, lest suddenly a contrary wind should stir and the sea rise into billows, and the ship be in peril, so Christians, even if they have in themselves a favorable wind of the Holy Spirit blowing, are nevertheless yet subject to fear, lest the wind of the adverse power should rise and blow on them, and stir disturbance and billows for their souls. There is need therefore of great diligence, that we may arrive at the haven of rest, at the perfect world, at the eternal life and pleasure, at the city of the saints, at the heavenly Jerusalem, at the church of the firstborn (Heb. xii. 23.). Unless a man gets through these measures, he is under much fear, lest in the meantime the evil power should effect some fall.
When you intend to do something and see that your thought is perturbed, and if after invoking God's Name it remains perturbed even by a hair's breadth, know from this that the action you mean to commit is from the evil one and refrain from commiting it. For nothing done with perturbation is pleasing to God.
Watch constantly, learning to understand God's law, for this warms the heart with heavenly fire. Guard your lips from the idle word, or empty talk, lest the heart gets used to evil words.