Within the Mystery of the Mass, there is no mystery in the first act that the people of God do in union with the priest.  The priest says:  Brothers and Sisters let us call to mind our sins, and prepare ourselves to celebrate the sacred Mysteries.

It is only with a contrite heart that one can begin to approach our Lord.  We do not present ourselves with the Pride of entitlement, nor the despair of the condemned.  But we confess equally with one another, to one another and in union with the Saints that we are sinners.  The first action is to call to mind that we have sinned and are in need of the saving Graces of our Lord.