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.
When you go to your spiritual father for confession, do not bring yourself as an accuser of other people, saying, 'he said this,' and 'so-and-so said that'. . . but speak about your own doings, so that you may obtain forgiveness.
The Lord commands all men to repent (Matt. 4:17), so that even the spiritual and those making progress should not neglect this injunction and fail to give attention to the smallest and most subtle errors.
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.