Christ's greatest gift to mankind was His sacrifice of His life for us and His greatest gift was to leave Himself in the Eucharist that we might have His physical presence with us forever.
"But I tell you the truth, it is to your advantage that I go away; for if I do not go away, the Helper will not come to you; but if I go, I will send Him to you (John 16:7 NASB).
Per the Word He has given us the Helper to be with us.
The Mass is a re-sacrifice of Christ again and again and again and again and again, etc, etc, etc.
He died one time for us....He doesn't need to continue to be sacrificed. This is the error of Roman Catholicism.
We don't need Christ's physical presence with us, especially bound up in little wheat wafers people have to eat to access Jesus.
He sent His Holy Spirit to dwell in the hearts of believers forever, thus enabling us to do greater works that His.
It's the Spirit who gives life, so that when the Holy Spirit enters the believer's heart through faith, He seals us for the day of redemption, thus securing our salvation FOREVER, not until we need to eat Jesus in a wafer again.