“It is better for you that I go. For if I do not go, the Advocate will not come to you.” (John 16:7)
  
Jesus promised the disciples that he would not leave them as orphans, therefore he spoke to them after His resurrection, “I am with you always, until the end of age."

Specifically, Jesus left us the Eucharist and His holy blood as a memento. With the power of Holy Spirit, the Church continues the offering of redemption: "This is my body that is for you. Do this in remembrance of me…this cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me." (1 Corinthians 11:23-25)

After the Pentecost, Paul spoke to the crowd, “God raised this Jesus; of this we are all witnesses. Exalted at the right hand of God, he received the promise of the Holy Spirit from the Father and poured it forth, as you (both) see and hear.” (Acts 2:32-33)

The work of the Holy Spirit is a continuation of the mission from the Father to the Son. “As a father has compassion on his children, so the LORD has compassion on the faithful.” (Psalm 103:13)

St. Paul's letter to Romans (Chapter VIII) explained fully that in the Holy Spirit Christians conquered sin and the flesh.It concludes that God has shown no regrets in having created human beings nor his redemptive work in saving mankind.