One of my parishioners asked me what this might mean, it is from the summary I put out on Sacramentum Caritatis.
“The pope cautions priests not to substitute themselves for Jesus. He exhorts them to celebrate the Mass with humility, “avoiding anything that might give the impression of an inordinate emphasis on his own personality.””
I think he might mean something like this:
This is a Mass celebrated by the Archbishop of Los Angeles, Cardinal Mahoney. Mahoney notoriously seems to break every liturgical law the Church has made, he seems to want to make the Church in the image of his own ego, not just by using glass vessels when the Church says these are outlawed, but the whole thrust of the liturgy seems to be horizontal, celebrating the community and celebrating himself. The Holy Father’s emphasis is “I must decrease, he must increase”. It applies to the celebrant and to the community as well, everything should point to Christ.
One of the worst examples I found on a quick search of You Tube was this Halloween Mass, where parishioners were encouraged to come in Halloween costumes, notice the woman Extraordinary Minister of Holy Communion with devil horns.
The whole reason for the Church having rules about the celebration of the Mass is to ensure that it doesn't become Father's, the Community's or even His Eminence's little show.