What did Jesus mean to give us at the Last Supper when he said, "This is my body?" In the Bible the word "body" doesn't indicate a component or part of a human being which, united to the other components, the soul and the spirit, forms the complete person. Our way of reasoning is influenced by Greek culture which, in fact, divided man in three parts: body, soul and spirit. In biblical terminology, and therefore in that used by Jesus and Paul, "body" indicates the whole human being in so far as it lives its life in a body, in a corporeal and mortal condition. In his Gospel, John uses the word "flesh" instead of "body" ("if you don't eat the flesh of the Son of man....") and it is obvious that this word in the sixth chapter of the Gospel means the same as in the first chapter where John says "the Word became flesh," and that is, human. The word "body" indicates, therefore, the whole of life. In instituting the Eucharist, Jesus left us the gift of his whole life, from the first moment of the incarnation to the very end, including all that had made up his life: silence, sweat, hardship, prayer, struggle, joy, humiliation....
Then Jesus also said: "This is my blood." What else does he give us with his blood if he has already given us all his life by giving us his body? He adds death! Having given us his life, he now gives us its most precious part - his death. In the Bible the term "blood" doesn't indicate a part of the body, and therefore a part of a part of a person; it indicates a happening, death. If blood is the seat of life as was thought at that time (cf. Gen 9:4), the shedding of it is the plastic sign of death. "Having loved his own who were in the world, he loved them to the end" (John 13:1). The Eucharist is the mystery of the Body and Blood of the Lord, that is of the life and death of the Lord!
And what do we ourselves offer when we offer our bodies and blood with Jesus at Mass? We offer what Jesus offered: life and death. By "body" we offer all that actually constitutes our physical life: time, health, energy, ability, sentiments, perhaps just a smile, that only a spirit living in a body can give and which is so precious at times. By "blood," we express the offering of our death; not necessarily our final death, or martyrdom for Christ or our brethren. Death means also all that right now prepares and anticipates our death: humiliations, failures, sickness that cripples us, limits due to age or health, everything that "mortifies" us. When St. Paul exhorts us by the mercy of God to present "our bodies," he didn't mean just our senses and carnal appetites, but all of ourselves, body and soul; especially our minds and our wills. In fact he goes on to say: "Do not be conformed to this world but be transformed by the renewal of your mind, that you may prove what is the will of God, what is good and acceptable and perfect" (Rom 12:2).
However, to conform to all this we must start practicing what we have said as soon as we come out from Mass. We must really make the effort, each one within his or her own limits, to offer our "bodies" to our brethren, and that is to say, our time, energy and attention - in a word, our lives. When Jesus had pronounced the words: "Take... this is my body; take... this is my blood," he didn't allow much time to pass before doing what he had promised: a few hours later he gave his life and blood on the Cross. Otherwise, it's all just empty words, lies. Therefore, after saying to our brothers and sisters: "Take, eat," we must really allow ourselves to be "eaten" and especially by those who do not act with the gentleness and kindness we expect. Jesus said: "What merit have you got if you love only those that love you, greet only those that greet you, invite only those that invite you? Everyone does this" (cf. Matt 5:46-47). On his way to Rome where he was to die a martyr, St. Ignatius of Antioch wrote: "I am the grain of Christ; that I may be ground by the teeth of wild beasts to become pure bread for the Lord." If we think about it, each one of us will realize that there are sharp teeth grinding us: criticisms, contrasts, hidden or open oppositions, different ideas in those surrounding us, differences in character. We should even be grateful to those who help us like this. They are of infinitely more benefit to us than those who approve or flatter us. In another letter, the same holy martyr wrote: "Those that praise me, scourge me."
... But we mustn't forget that we have also offered our "blood," and that is to say our passiveness, and mortification. It is when we can no longer do what we want that we can be closer to Christ. After Easter Jesus said to Peter: "When you were young, you girded yourself and walked where you would; but when you are old, you will stretch out your hands, and another will gird you and carry you where you do not wish to go. This he said to show by what death he was to glorify God" (John 21:18ff). Shortly before this Jesus had said to Peter three times: "Feed my sheep," but now he makes him understand that it is in dying that he will give the greatest glory to God.
Because of the Eucharist there is no such thing as a "useless life" in the world. No one should say: "What use is my life? What am I doing in this world?" You are in the world for the most sublime of reasons, to be a living sacrifice, to be Eucharist with Jesus.