The Holy Eucharist is the carnal intimacy between Christ and His Bride the Church. It is the exchange of Divine Love between Christ and His Beloved. He gives Himself to Her and becomes a part of Her and filled with Him She becomes a part of Him. In their carnal union, Christ and the Church become One Flesh. It is the antithesis of sin and as such the Devil hates it. It is the one thing in the world that is the most opposed to him and everything he stands for. Sin is merely separation from God; following your own will instead of His. Hence, sin and the Eucharist are irreconcilable. One cannot be in Christ and sin at the same time. To attempt to do so is hypocrisy, but being sinful when approaching for Communion is more than that, it actually impedes the exchange of Divine Love. How can you participate in the back and forth exchange of Divine Love with Christ if you do not have Divine Love within you?
Some, seeking to commit the sin of sacrilege with the Divine Eucharist, make excuse with excuses in sins saying that we are all sinners and thus if some can receive, all can receive. No! This is a lie. We are not all sinners. Those who have gone to Confession are not sinners. They are holy. They will remain that way until they sin again. Those who have sinned are sinners and will remain that way until they go to confession. Sinfulness is a temporary condition. It lasts only until you go to confession. After Confession you are not a sinner, but holy and will remain in that condition until you sin again. There is a reason why we hear at Divine Liturgy "Holy Things for the holy". Communion is for the holy and it is Confession that restores you to holiness after falling into sinfulness.
The Eucharist is the exchange of Divine Love between Christ and His Beloved and Confession restores you to Divine Love after being in sin. Hence, Communion is for the holy and Confession is for the sinful. Those two mysteries have mutually exclusive demographics. They are not the same and neither are the people for whom those mysteries exist. Why is this distinction between the holy and the sinful so black and white and so important? Because those who die while holy go to Heaven and those who die while sinful go to Hell. "But what about purgatory?", some say in a whiny voice. Purgatory (which is a lake of fire) is just a way for us to try and explain the post-mortem purification for those who are holy, but haven't yet reached the perfection of holiness. (While purgatory is a much newer way of explaining post-mortem purification than the Toll-Booths, it does make much more sense, at least to me.) Post-mortem purification is no more permanent than this life, so that's no cop-out. Regardless of everything, in the end, everyone will be either among the sheep or the goats; everyone will be in either Heaven or Hell.
Some, also seeking to make excuse with excuses in sin, say that none of us are worthy, hence, if some can receive, all can receive. No! What do we chant for a man when he is ordained? AXIOS! Axios means "worthy" or "he is worthy". Similarly, the troparion of Christ the Bridegroom ascribes the vigilant soul as worthy and the slothful soul as unworthy. Not all are unworthy. God does not commit sacrilege with His own gifts. People on earth might want to commit sacrilege with God's gifts, and do so in many ways, but God does not. When He gives Divine Grace to someone in any of the mysteries, it is because that person has proved himself worthy. Those baptized have proved themselves worthy by professing faith in the Church. Those absolved in Confession have proved themselves worthy by repenting of their sins (as opposed to being unrepentant). Those receiving Communion have proved themselves worthy by going to Confession and remaining pure afterwards.
We do not exist for the mysteries, the mysteries exist for us. They exist to strengthen us in different ways, each according to different conditions a person might be in, whether it be purification for the sinful in confession, strength for the holy in Communion, and so on. If the mysteries exist for us, then we are worthy of them. God calls all men to salvation through the mysteries of the Church. There are no other means of salvation, since in the holy mysteries, there is all help for all people, each according to his own kind. The only problem that can arise then is if someone in one condition tries to grab the mystery designed for another person. In their pride they delude themselves with a fake union that does not exist, since they are not properly disposed for that mystery and it is not for them. Each mystery is for a different specific purpose. The sin of lust, more than any other, impedes the mysteries, not only because it is the most common sin by far, but also because it is a direct parody of the exchange of Divine Love in Holy Matrimony, committing sacrilege against the flesh, which is designed for that exchange.
Sin is separation from God and Holy Communion is union with God. Not only is it hypocritical to try and have both, it is downright delusional. Holy Communion is not a tool for people to manipulate to support their sins. It is God Himself. Holy Communion is the expression of Divine Love between Christ and those who are already in His Love. Baptism and Confession are what Christ established for those outside His Love. Christ came to convert us from our sins and join us to Himself. He did not come to support the lives we were already living. If that was so, then His coming would have been for nothing.