Why do I have to receive the Sacrament of Confession after committing a mortal sin before I can receive the Eucharist?
When in a state of mortal sin the sin corrupts the purity of our soul and prevents us from receiving the grace that the Eucharist brings to us by consuming the Body and Blood of Christ. When we receive Jesus we have to have our whole hearts and whole minds available to him, but if we have a grave sin on our conscience and within our hearts it acts as a barrier that does not allow the light of Christ to penetrate through, and then we cannot share that light with others. Only the Sacrament of Confession can tear down that barrier and enable us to receive the grace promised to us by the Eucharist.
When we are baptized we receive grace as Catholics, and mortal sin takes away the grace that can only be restored by the Sacrament of Penance. If we are no longer in a state of grace due to mortal sin how could we then receive more grace from the Eucharist? It would not make sense that we can receive the grace promised to us in the Eucharist if our relationship with Christ needs to be reconciled and we still need healing for our hearts and minds.
Can't God just forgive me?
I recall from a homily once given by a priest explaining how we as human beings by our very nature need to be able to free ourselves from heavy burdens that we hold deep down in our hearts and we desire to be able to obtain forgiveness. Jesus understood the need that we have to be able to receive the powerful sense of freedom by being able to talk out loud to someone else about what is burdening us. I know in my own experience simply by talking to someone after going through a challenging or difficult experience I always feel so much better to be able to get the words out by speaking to a friend or family member.
The Sacrament of Penance not only give us the ability to discuss our transgressions, it also gives us the ability to be forgiven. After walking out of the confessional I always feel this amazing sense of knowing that I now can start anew, and have a fresh start in working to keep strong my relationship with Christ because now I can truly let go of my sins. After my last confession the line from the Frozen song, "Let it Go" came to mind:
"Let it Go, let it go. Turn away and slam the door"!
Once we leave the confessional the sacrament truly frees us from our sins, and we do need to let them go to be able to embrace and accept the grace given to us by the sacrament. Jesus gave the disciples by the power of the holy spirit the ability to forgive sins. Why would Jesus give the disciples that power and then not want that power to be passed on through the generations? Why would Jesus want the people of his time to be able to have the burden of their sins lifted from them and yet today not want that for us?
When we confess our sins to a Catholic priest and receive absolution we are set free. Our hearts and minds are no longer held captive by our sins and we receive the grace to reconcile our relationship with both God and our Church. When we commit sin, especially grave sin, we affect the entire body of Church, and we affect all of our brothers and sisters in Christ by weakening our relationship together as "One, Holy, Catholic, and Apostolic Church".