Pope Benedict 16:

"In the Eucharist Christ wanted to give us his love, which impelled him to offer his life for us on the Cross.

At the Last Supper, in washing the disciples' feet, Jesus left us the commandment of love: 'even as I have loved you, that you also love one another' (Jn 13:34).

However, since this is only possible by remaining united to him like branches to the vine (cf. Jn 15:1-8), he chose to remain with us himself in the Eucharist so that we could remain in him.

When, therefore, we nourish ourselves with faith on his Body and Blood, his love passes into us and makes us capable in turn of laying down our lives for our brethren (cf. 1 Jn 3:16)

. . . . From this flows Christian joy, the joy of love and the joy to be loved." 

Angelus March 18, 2007 in The Eucharist: Spiritual Thought Series 2009, p. 91.