Catechism of the Catholic Church
“By the same charity that it enkindles in us, the Eucharist preserves us from future mortal sins. The more we share the life of Christ and progress in his friendship, the more difficult it is to break away from him by mortal sin. The Eucharist is not ordered to the forgiveness of mortal sins – that is proper to the sacrament of Reconciliation. The Eucharist is properly the sacrament of those who are in full communion with the Church.”
Source: Catechism of the Catholic Church #1395