If the Blessed Mother and St. John at the foot of the Cross had closed their eyes when Our Lord was offering Himself for the sins of the world, the spiritual effects on them would have been no different from those which we may receive as we assist at the Sacrifice of the Mass. But if their eyes were open, there would have been this difference: they would have seen the sacrifice offered in bloodshed with blood pouring from gaping holes in hands and feet and side. In the Mass, we see it performed without bloodshed.

The Mass, therefore, is not a substitute for the Cross, but the merit we gain at the Mass is the same as the merit we would have gained if we had assisted at Calvary.

A Fulton Sheen Reader
Bishop Fulton Sheen