Not ultimately the Eucharist from the Cross, but the Cross from the Eucharist

"everything that follows the Last Supper receives a new meaning; it takes its meaning from Jesus' decision to give his eucharistic Body unconditionally, that is to say, to give the totality of his personal history, which culminates in the paschal mystery, for his Bride, whom he makes his ecclesial Body.  The subsequent events—the suffering—follow the preceding events—the action—not only chronologically, but flow from them as an effect flows from a cause.  The Eucharist does not have its source in the cross (as a rather narrow-minded version of the holy sacrifice of the Mass would have it); to the contrary, the cross has its source in the Eucharist, understood as the irrevocable decision made by Jesus on the evening of Holy Thursday and attested to by the institution of the memorial before the events they memorialize...."

Jean-Pierre Batut, "Believing in the resurrection, or:  the logic of love," trans. Michelle K. Borras, Communio:  international Catholic review 37, no. 1 (Spring 2010):  43 (34-46).  Furthermore, "This radical absence of any kind of gap between the love expressed and the love given. . . . allows us, whose decisions are so often irresolute and whose fickleness ceaselessly calls into question the most irreversible gifts, to draw from the Lord's fidelity and not from our own resources the capacity for a fidelity to which we aspire, all the while knowing that we are incapable of it."