Pope St. John Paul II
“The priest is quite aware that he cannot count on his own efforts to achieve the purposes of his ministry. Rather, he is called to serve as an instrument of the victorious action of Christ whose sacrifice, made present on the altars, obtains for humanity an abundance of divine gifts. However, he also knows that, in order worthily to pronounce the words of consecration in the name of Christ–‘This is my Body…. This is the cup of my Blood’–he must be profoundly united to Christ and seek to reproduce Christ’s countenance in himself. The more intensely he lives in Christ, the more authentically he can celebrate the Eucharist.”
Source: Pope St. John Paul II, General Audience, June 9, 1993