Bishop Kallistos of Diokleia, quoting St Ignatius:

The Church is a Eucharistic society, a sacramental organism which exists in all its fullness whenever the Eucharist is celebrated. It is no coincidence that the Body of Christ should mean both the Church and the Sacraments and that the phrase communio sanctorum should mean communion of saints and communion in the sacraments.

(p. 242, The Orthodox Church, 1997)

The entire NT theology is premised around unity and participation. Christ who is embedded in the ecology of the earth with us, a rather nice way of talking about the incarnation, the Holy City inhabited by God that descends from heaven dressed like a bride (and whose birthday we celebrate today).