It is the Eucharist that constructs the Church. It is in the celebration of the Eucharist that we become Church. Church is a gift given to us, not something of our own construction.
Church is the fruit of the gratuitous love of God which becomes visible in Jesus Christ, who loved us first and who died for us and rose again so that we can have life. Eucharist is the apex, the highest expression of Christian existence and it is the bond which links faith and life.
We celebrate the Eucharist "in memory of me". Our priesthood, our entire Christian existence assume their deepest expression when they too become the celebration of the "memory of Jesus Christ".