#36. Along these same lines, the Catechism of the Catholic Church rightly stipulates that “anyone conscious of a grave sin must receive the sacrament of Reconciliation before coming to communion.” I therefore desire to reaffirm that in the Church there remains in force, now and in the future, the rule by which the Council of Trent gave concrete expression to the Apostle Paul’s stern warning when it affirmed that, in order to receive the Eucharist in a worthy manner, “one must first confess one’s sins, when one is aware of mortal sin.”
#37 The judgment of one’s state of grace obviously belongs only to the person involved, since it is a question of examining one’s conscience. However, in cases of outward conduct which is seriously, clearly and steadfastly contrary to the moral norm, the Church, in her pastoral concern for the good order of the community and out of respect for the sacrament, cannot fail to feel directly involved. The Code of Canon Law refers to this situation of a manifest lack of proper moral disposition when it states that those who “obstinately persist in manifest grave sin” are not to be admitted to Eucharistic communion.
#48 The bread which is broken on our altars, offered to us as wayfarers along the paths of the world, is panis angelorum, the bread of angels, which cannot be approached except with the humility of the centurion in the Gospel: “Lord, I am not worthy to have you come under my roof ” (Mt 8:8; Lk 7:6).
You can read the entire encyclical Ecclesia De Eucharistia at vatican.va/content/john-paul-ii/en/encyclicals/documents/hf_jp-ii_enc_20030417_eccl-de-euch.