When Should I Abstain from Holy Communion?

Q: A certain Christ-loving man asked the same Elder: Should one be curious about the Divine Mysteries? And is a sinner who approaches them condemned as unworthy?

A: When coming into the holy temple to receive the Body and Blood of Christ, and when receiving Them, pay heed to yourself that you unfailingly believe the truth of this (Sacrament). But as to how this happens, do not be curious, as it has been said “Take, eat, This is My Body and Blood.” The Lord gave them to us for the remission of sins (Matt. 26:26; Mark 14:22). We have hope that he who believes thus will not be condemned, but he who does not believe is already condemned. And thus, do not forbid yourself to approach, condemning yourself as sinner, but recognize that a sinner who approaches the Savior is vouchsafed the remission of sins. (Saints Barsanuphius and John: Guidance toward Spiritual Life, p. 111)