When Jesus was about to ascend into heaven, he said:
And I will ask the Father, and he will give you another Advocate to be with you always, the Spirit of truth, which the world cannot accept, because it neither sees nor knows it. But you know it, because it remains with you, and will be in you. I will not leave you orphans; I will come to you.
— The New American Bible (NABRE), 2011, John 14:16-18
The Advocate, the holy Spirit that the Father will send in my name – he will teach you everything and remind you of all that (I) told you.
— NABRE, 2011, John 14:26
“When the Advocate comes whom I will send you from the Father, the Spirit of truth that proceeds from the Father, he will testify to me.
— NABRE, 2011, John 15:26
But I tell you the truth, it is better for you that I go. For if I do not go, the Advocate will not come to you. But if I go, I will send him to you. And when he comes he will convict the world in regard to sin and righteousness and condemnation: sin, because they do not believe in me; righteousness, because I am going to the Father and you will no longer see me; condemnation, because the ruler of this world has been condemned. Coming of the Advocate “I have much more to tell you, but you cannot bear it now. But when he comes, the Spirit of truth, he will guide you to all truth. He will not speak on his own, but he will speak what he hears, and will declare to you the things that are coming. He will glorify me, because he will take from what is mine and declare it to you. Everything that the Father has is mine; for this reason I told you that he will take from what is mine and declare it to you.
— NABRE, 2011, John 16:7-15
These quotes from the Gospel of John showed the role of the Holy Spirit in our lives. Jesus stated that He will not leave us an orphans, but rather send the Holy Spirit to walk with and guide us.
The Catechism of the Catholic Church confirms the role of the Holy Spirit:
“The One whom the Father has sent into our hearts, the Spirit of his Son, is truly God. Consubstantial with the Father and the Son, the Spirit is inseparable from them, in both the inner life of the Trinity and his gift of love for the world. In adoring the Holy Trinity, life-giving, consubstantial, and indivisible, the Church’s faith also professes the distinction of persons. When the Father sends his Word, he always sends his Breath. In their joint mission, the Son and the Holy Spirit are distinct but inseparable. To be sure, it is Christ who is seen, the visible image of the invisible God, but it is the Spirit who reveals him.”
—- Catechism of the Catholic Church (CCC), 2000, para.689