In the case of the Eucharist, it is the blessing placed on the bread and wine that is ingested and becomes a part of your body through the miracle of FAITH. The words of blessing and thanksgiving are placed on the species and become a part of the faithful. It isn't just an “oh, remember when” moment. It is the blessing Christ pronounced over the bread and wine that became the bread of life. His words satisfied all hunger and longing for knowledge of God. It is the substance He chose to use as the sacred covenant between Himself and us (which, by the way, had He chosen liver and onions, I'd have choked it down). It is the visible touchstone with the Divine and made a part of us. It is totally dependent on being in complete charity with God the Father and the faith in the Lord Jesus, Christ.
We can bang on about whether it is or isn't necessary to think the substance of the bread and wine changes, but God's DNA is in everything and thereby (through one bread and one body and the cup of blessing which we bless) that He becomes united with our own DNA. Baptism of the Lord wasn't about cleansing Him of sin, it was about baptising the water which all flows into one sea and throughout the world. It waters the grain and the grapes and through our FAITH returns to us and we to our Maker.
That's what I think it is all about. Being one in the body of Christ through FAITH.