“The conscience is cleansed by repentance: consequently it is necessary to repent unceasingly. For repentance cleanses all pollution from the soul and makes it pure (1 John i. 9). Repentance does not just consist in the words, ‘Forgive, O Lord; have mercy, O Lord’. To receive remission of sins we must also realize to the full the definite impurity of each thought, glance, and word, of each kind of allurement, we must be conscious of our own guilt and of our own lawlessness and absence of justification, we must recognize our need to pray for God’s forgiveness, until the spirit attains peace.
As far as great sins are concerned, they must be confessed immediately to our spiritual father and pardon obtained, because in the case of such sins we cannot restore peace to our spirit simply by daily acts of repentance in our private prayers. Therefore the duty of continual repentance is the same as the duty of keeping our conscience pure and irreproachable.” (St. Theophan the Recluse in The Art of Prayer: An Orthodox Anthology, pg. 228)