I was lucky enough to be at the Cathedral today to celebrate Corpus Christi. The (rather diminished) choir sang Aquinas' exquisite texts for the feasts, to a variety of musical settings. The mass was ended with a short procession around the body of the Church and Benediction of the Sacrament.
There is something very humbling seeing a body of people kneel before a piece of bread. If it were anything other than what the Church teaches the Eucharist to be, then the whole exercise would have been the worst of blasphemies; and yet Jesus' stark and unbending words in the Gospels - "This is my body" - reassure me that we were not adoring mere bread.
The Latin origin of the word "sacrament" originally meant "pledge" or "oath". One of the reasons the Roman authorities were so suspicious, so I am told, of the Early Church is because Christians were observed to take "sacraments" as a group: to the Emperors this sounded like a revolutionary secret society! One can easily imagine the Roman establishment being fearful of Christians in the same way that the Papacy and Austria were fearful of the carbonari eighteen-hundred years later.
But a pledge is exactly what the Eucharist is. In John Wesley's Eucharistic hymn "Victim divine", of 1786, even an ardent Protestant observes that "Thou art to all already given... and shew thy real presence here." The joys of heaven which we will receive in the future are given to us in the consecrated elements in our here and now.
It is a privilege to observe this. As I'm not in communion with Rome (yet), it is moving to watch people return from the altar; some weep, others smile to themselves as if enjoying the company of an old friend, others simply whisper to the God they have received.
It is right and proper that there should be a day set aside to thank God for this great and life-giving mystery.