The Church sets out specific guidelines regarding how we should prepare ourselves to receive the Lord’s body and blood in Communion. To receive Communion worthily, you must be in a state of grace, have made a good confession since your last mortal sin, believe in transubstantiation, observe the Eucharistic fast, and, finally, not be under an ecclesiastical censure such as excommunication.
A mortal sin is any sin whose matter is grave and which has been committed willfully and with knowledge of its seriousness. Grave matter includes, but is not limited to, murder, receiving or participating in an abortion, homosexual acts, having sexual intercourse outside of marriage or in an invalid marriage, and deliberately engaging in impure thoughts (Matt. 5:28–29). Scripture contains lists of mortal sins