+JMJ+
So let me get this straight: you want to discuss whether you are wrongly assuming about sanctifying grace, but you do not want to talk about what you know about it? Really? Especially when I see some errors about what you know about it, like the Catechism itself saying that you cannot have absolute certainty of the presence of sanctifying grace (CCC 2005), nor is there any requirement for anybody to have sanctifying grace to receive Holy Communion, only that one should have (among other requirements) no conscious knowledge of grave sin without previous Sacrament of Reconciliation (Code of Canon Law, CIC 916).
Besides how about mortal sin that you are not aware of, like pride? Pride is dangerous in that it blinds you from your own sinfulness. Remember the parable about the Pharisee and the tax collector (Luke 18:9-14)?
I do not know about St Therese not being conscious of any mortal sin in her life, but this is what she said: “Make it clear, Mother, that if I had committed all possible crimes, I would still have the same confidence. I would feel that this multitude of offenses would be like a drop of water cast into a blazing fire.”
2005 Since it belongs to the supernatural order, grace escapes our experience and cannot be known except by faith. We cannot therefore rely on our feelings or our works to conclude that we are justified and saved.56 However, according to the Lord’s words "Thus you will know them by their fruits"57 - reflection on God’s blessings in our life and in the lives of the saints offers us a guarantee that grace is at work in us and spurs us on to an ever greater faith and an attitude of trustful poverty.
That doesn’t say we can’t know that we are in the State of Sanctifying Grace, it says we cannot rely on our feelings or works to conclude that we are justified and saved. That is completely different. In fact, it’s saying we
can know by Faith. The basis of this entire passage is essentially “Don’t be Pelagian”.
And you are wrong. The Church explicitly states that if we receive the Eucharist in mortal sin, that is a grave sacrilege. Saint Paul says if you eat and drink the Body and Blood of our Lord unworthily (I.e., in mortal sin) you eat and drink damnation unto yourself. Therefore, you must be in a state of sanctifying grace in order to receive communion. If that’s not enough, this is Catholic Answers itself saying you must be in the state of sanctifying Grace to receive communion:
catholic.com/tracts/who-can-receive-communion
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First, you must be in a state of grace. “Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of profaning the body and blood of the Lord. Let a man examine himself, and so eat of the bread and drink of the cup” (1 Cor. 11:27–28). This is an absolute requirement which can never be dispensed. *To receive the Eucharist without sanctifying grace in your soul profanes the Eucharist in the most grievous manner. *
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 (for example, 1 Cor. 6:9–10 and Gal. 5:19–21). For further information on what constitutes a mortal sin, see the Catechism of the Catholic Church."
As for mortal sin we are not aware of, that is impossible. The Catechism explicitly states that three things are necessary for mortal sin: Grave matter, consent, and
knowledge that it is a mortal sin. Therefore, you cannot commit a mortal sin and not realize it. Every mortal sin is purposefully committed with full knowledge and consent. If either of those two things are not present, it is not mortally sinful and you are in the state of sanctifying grace.