If then you are the body of Christ and his members, it is your sacrament that reposes on the altar of the Lord… Be what you see and receive what you are
St. Augustine, Sermon 272
Because it is the memorial of Christ’s Passover, the Eucharist is also a sacrifice. The sacrificial character of the Eucharist is manifested in the very words of institution: “This is my body which is given for you” and “This cup which is poured out for you is the New Covenant in my blood.” In the Eucharist Christ gives us the very body which he gave up for us on the cross, the very blood which he “poured out for many for the forgiveness of sins.” CCC 1365
The mode of Christ’s presence under the Eucharistic species is unique. It raises the Eucharist above all the sacraments as “the perfection of the spiritual life and the end to which all the sacraments tend.” In the most blessed sacrament of the Eucharist “the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained.” “This presence is called ‘real’—by which is not intended to exclude the other types of presence as if they could not be ‘real’ too, but because it is presence in the fullest sense: that is to say, it is a substantial presence by which Christ, God and man, makes himself wholly and entirely present.” CCC 1374