Mass as sacrifice
We as Christians do believe that the Mass does participate in the everlasting sacrifice of Christ. In Hebrews 25-28 it reads, "Not that [Christ] might offer Himself there again and again, as the high priest enters year after year into the sanctuary with blood that is not his own; if that were so, He would have had to suffer death over and over from the creation of the world. But now He has appeared at the end of the ages to take away sins once for all by His sacrifice. Just as it is appointed that men die once, and after death be judged, so Christ was offered up once to take away the sins of many; He will appear a second time not to take away sin but to bring salvation to those who eagerly await Him." The mass is almost like a memorial.