This ancient practice survives today when the priest breaks the consecrated host, and immediately places a small part of it into the chalice. When he does so, he ritually recognizes that although we are separate from the whole body of Christ, by time, by geography, by death and sometimes by human disagreements and strife, still there is an underlying unity in the Body of Christ.
What is vital to remember is that the more we, as individuals, submit to the simple teachings of the church, the more we grow together in unity. The more we push our own agendas, disagree, pick fights with others and ‘un-church’ others, the more we sin against unity, and in so doing, sin against the Body of Christ.
These thoughts are gleaned from my reading of Mgr. Guissani’s The Journey to the Truth is an Experience.