Another meandering walk through my amateur understanding of theology…
I was listening to a talk by Mother Margaret Mary, the founder of the Children of Mary community in Ohio (they have a channel on Youtube), and she was talking about the way in which many Catholics understand (or rather don't) what we call the True Presence of Christ in the Eucharist. (I have no idea if I've posted the right video, but that's ok because everything Mother Margaret Mary says is AWESOME.) She was at a church for a Eucharistic Holy Hour and afterward saw the two young altar servers. She said something like, "isn't that wonderful to be able to serve Jesus when he's really present in the Eucharist?" They agreed. Then she asked what that means to them, that he's really present. "Is he really there, like your parents who were there? Or is he really there in spirit? Or is it a symbol of him really being there?" And they said "Ummm… I guess it's a symbol." GAH!!! That's not at all what the Real Presence of Christ means. Quite literally, it means that he's REALLY there.
Catholics believe that during the Mass when the priest speaks the words that Jesus spoke at the Last Supper (this is my body, this is my blood) the wafers and wine literally become his body and blood even though they still look, smell, feel and taste like wafers and wine--thank God for that because it would be much harder for me to drink from a cup of what looks, smells and tastes like blood! Some super geniuses have explained how such a change, referred to as transubstantiation, could come about (e.g. St. Thomas Aquinas). But it's not like drinking blood and eating flesh in a cannibalistic way. The whole Jesus is present in any fragment of wafer or drop of wine. I like to think of it as the mini-Jesus, who gets mini-er the smaller the drop of wine becomes. Once the presence of the consecrated bread/wine is gone (for example, I've digested it or it has been petrified or burned into ashes or whatever) then the mini-Jesus is also gone. Where does he go? Same place he was before, I guess, he's just no longer physically present in me. I don't know, that's why it's called a mystery. But what is he doing while he's inside of me? (Is he singing songs like Jonah?) What does it matter that he is physically present within me?
When I'm in a state of grace and receive Holy Communion, Jesus comes into my body in a special way for the period of time during which my body digests the host. Jesus himself said that his body is true food and his blood is true drink. It has a nourishing effect. The scripture also says that he will make his enemies his footstool. While he's in there he starts making whatever enemies he finds into his footstool, conquering them one by one. He also heals any wounds he finds. Essentially, he gradually makes us holy and transforms us into himself (you really are what you eat!). But his power to do this depends on my openness to his grace and belief in his power to do so. If I am weak in faith the effect will be small, not because Jesus is weak but because I have in a sense not given him permission to use his full strength. And God does not force himself on anyone.
Let's say I have been trying to give up some venial sin, like complaining about the weather. If I start receiving Holy Communion every day, Jesus will continue his healing work and make it easier over time for me to stop doing that. Whatever inside of me makes me want to complain will become weaker and weaker as Jesus makes his enemy his footstool. However, each time I complain I am in some sense choosing the enemy over Jesus. If the sin is venial, and so I have not made a conscious decision for the enemy or a conscious decision to offend God, then Jesus will take away the sin the next time I attend Mass. Even so, it is beneficial for me to take advantage of the Sacrament of Penance and Reconciliation which will strengthen me even further to avoid this sin in the future and will provide extra healing for the negative effects of that sin. Why not fight with every weapon available?
However, when I commit a mortal sin, I am no longer in a state of grace. Then I have allowed death and darkness to enter in and take the place of the light and life that are the presence of the Holy Trinity. In a sense I have given the enemy permission to do his destructive work inside of me. It's not the same as possession, in which I've literally given a spirit permission to take over my will. But I've taken the devil's medicine which can only harm my soul. If I committed the act willingly and knowing that the Church believes it to be a sin then I have chosen the enemy over God regardless of what excuses I make to rationalize my action. It doesn't matter if I think that God shouldn't be offended what I've done, who knows the mind of God? Sin often looks good to us. (Even Satan can appear as an angel of light!) I have no choice but to trust the Gospels and the Church.
After committing a mortal sin, I must not receive communion! Not only would it be an offense against God but I have, in a sense, revoked the permission I gave for Jesus to act within me so receiving communion can no longer do me any good. And so, in a way, Jesus is left powerless against the enemies within me--not because he is powerless, but because of the weakness of my faith. ("Jesus could not do any miracles there. […] He was amazed at their lack of faith." Mark 6:5-6) Instead of healing and defending me, he is sent back to the agony in the garden where he sees that his precious gift of self has been scorned and rejected. My unworthy communion is Judas' kiss for Jesus. Thus the effect of communion on my being is actually the opposite of what it was before and, as St. Paul said to the Ephesians, "You drink condemnation on yourselves. This is why so many of you are dying." It is sin and the rejection of God that brought death into the world in the first place.
If we have died with him, we shall also live with him;
if we persevere, we shall also reign with him.
But if we deny him, he will deny us.
If we are unfaithful, he remains faithful,
for he cannot deny himself.
2 Timothy 2:11-13
Through mortal sin, I break my covenant with God. A covenant is a binding agreement. Giving my life to Jesus is binding. But when I have broken this covenant it is no longer binding, and no amount of well wishing will change that. God allows there to be consequences to our actions. Just as I originally had to go to the Church for Baptism in order to pass from death to life, I now have to return to the Church for the Sacrament of Reconciliation to reinstate my Baptismal covenant and to enter again from death to life. (Although it's not theologically sound, it can be helpful to think of it as though I've unbaptized myself.) Until I have gone to the Church for this Reconciliation I'm still in the realm of death and not in a state of grace. Therefore, it is foolish for me to receive Holy Communion, which will only do greater harm.
If something keeps me from returning to the state of grace (for example, if I am in a second marriage and have not yet found a way to rectify the situation), then I should remind myself that God's mercy is infinite and have hope that he will allow me to enter the Kingdom of Heaven. However, I should NOT presume God's mercy and act as though I am in a state of grace when I know that I am not. In this case, the Church recommends that I make a spiritual communion. Many Saints have indicated that a spiritual communion can be as efficacious as a physical communion when one has the proper interior disposition.
Here is a great article by a woman who is remarried and handling the situation in the best way she can:
Even outside of the state of grace, I can adore Jesus in the Eucharist. Spending time in Eucharistic Adoration is beneficial for everyone, even the unbaptized. I know because I used to make a Eucharistic Holy Hour every morning during RCIA. I could feel a calm and a peace within the adoration chapel that I was sure came from the physical presence of Jesus. If simply touching his garment could heal a lifelong affliction, then what miracles of grace will come through sitting in his presence?
During my year of preparation for Baptism, I felt encouraged that if I were to die before my official entry into the Church then God would grant me the grace of Baptism by Desire. The authority of the Church maintains that this mercy is extended to those who die as catechumens, with a clear intent of being Baptized. Certainly the same goes for those who are killed for the faith during preparation for Baptism, as was the case with Saints Felicity and Perpetua who received the Baptism by Blood. I have great hope that a person who is not in a state of grace but who is obeying the teachings of the Church when it comes to the Holy Eucharist (i.e. not receiving) and who desires to return to full communion with the Church would receive an abundance of God's mercy if he/she died before absolution could be obtained through the Sacrament of Reconciliation.
I have great respect for those who, although not currently in a state of grace, maintain respect for the authority of the Church and the True Presence of Christ in the Eucharist while hoping in God's mercy. May we one day all be in perfect communion!