How Can We Change the World?

The answer is shockingly simple. It is to strive to live lives of holiness and charity. Pope Benedict provides us, in Sacramentum Caritatis with beautiful expositions of why the Eucharist is the key to this:

Christianity's new worship includes and transfigures every aspect of life: "Whether you eat or drink, or whatever you do, do all to the glory of God" (1 Cor 10:31). Christians, in all their actions, are called to offer true worship to God. Here the intrinsically eucharistic nature of Christian life begins to take shape. The Eucharist, since it embraces the concrete, everyday existence of the believer, makes possible, day by day, the progressive transfiguration of all those called by grace to reflect the image of the Son of God (cf. Rom 8:29ff.). There is nothing authentically human – our thoughts and affections, our words and deeds – that does not find in the sacrament of the Eucharist the form it needs to be lived to the full. Here we can see the full human import of the radical newness brought by Christ in the Eucharist: the worship of God in our lives cannot be relegated to something private and individual, but tends by its nature to permeate every aspect of our existence. Worship pleasing to God thus becomes a new way of living our whole life, each particular moment of which is lifted up, since it is lived as part of a relationship with Christ and as an offering to God. The glory of God is the living man (cf. 1 Cor 10:31). And the life of man is the vision of God.