Well, then, remember that when we receive Communion, we become the monstrance in which Our Lord tabernacles. Our very bodies and souls become the receptacles for the Second Person of the Trinity. And that's why we need the Sacrament of Confession. Because otherwise, when we receive the Eucharist, we're placing it in the pit of filth inside of us. And Christ makes it absolutely clear that He'd rather you had unclean hands than an unclean heart. In Mark 7, the Pharisees complain that the Disciples are eating with unclean hands. Jesus uses this incident to show what really matters (Mark 7:14-23):
So yes, it'd be a shame and a disgrace for someone to put the Eucharist into a filthy Monstrance. But far worse would be our receiving Christ without having gone to Confession for all of the evil thoughts and deeds we've committed. And just as it'd be our basic Christian duty to (politely) confront a priest who put the Eucharist is physical filth, we seem to have a similar duty to (politely) confront those we know are putting the Eucharist into spiritual filth. Those aren't easy conversations to have. But if we really care about the proper respect shown for the Eucharist (even a little bit), it's the right thing to do.Again Jesus called the crowd to him and said, “Listen to me, everyone, and understand this. Nothing outside a man can make him ‘unclean’ by going into him. Rather, it is what comes out of a man that makes him ‘unclean.’”
After he had left the crowd and entered the house, his disciples asked him about this parable. “Are you so dull?” he asked. “Don’t you see that nothing that enters a man from the outside can make him ‘unclean’? For it doesn’t go into his heart but into his stomach, and then out of his body.” (In saying this, Jesus declared all foods “clean.”)
He went on: “What comes out of a man is what makes him ‘unclean.’ For from within, out of men’s hearts, come evil thoughts, sexual immorality, theft, murder, adultery, greed, malice, deceit, lewdness, envy, slander, arrogance and folly. All these evils come from inside and make a man ‘unclean.’”
Finally, St. Paul writes, in 1 Corinthians 11:27-31,
Of course, the people Paul is writing to aren't physically dead or asleep. What he's saying is that they're spiritually ill, and even spiritually dead, from their lack of respect for the Eucharist. In partaking of the Eucharist in an unworthy manner, they're sinning against the Body and Blood of Christ Himself. Paul describes it as eating and drinking damnation upon ourselves. That's a vivid and terrifying image.Therefore, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the body and blood of the Lord. A man ought to examine himself before he eats of the bread and drinks of the cup. For anyone who eats and drinks without recognizing the body of the Lord eats and drinks judgment on himself. That is why many among you are weak and sick, and a number of you have fallen asleep. But if we judged ourselves, we would not come under judgment.
St. Paul's response to this is simple and worth remembering: do an examination of conscience before you present yourself for the Eucharist. If you've got mortal sin on your conscience, go to Confession before you receive (James 5:16; John 20:21-23). The Eucharist will still be there after you go, and you've got nothing to gain (and a lot to lose) by trying to receive Christ before your soul is prepared for Him. Trying to put new Wine into old wineskins causes the old wineskins to burst (Matthew 9:17). So make sure you've become the proper receptacle to receive Christ before you attempt to. If we would only follow this simple advice - if we would just examine and judge ourselves before going to receive - we'd find our lives spiritually enriched from the Sacraments, and we wouldn't come under the Judgment of God.