The Holy Spirit confirms and strengthens us. He makes us confident, bold, and immune to manipulation by fears. Peter, for example, before receiving the Spirit, denied Christ three times when he was confronted with very minimal pressure from a servant girl (Lk 22:56ff). After receiving the Spirit, Peter fearlessly proclaimed Jesus as Lord and Savior without being intimidated by a formidable group of leaders, elders, scribes, and members of the high priest's family (Acts 4:5-6).
How does the Spirit change "chickens" into fearless warriors for God? The Spirit from our hearts cries out "Abba!" ("Father") (Gal 4:6; Rm 8:15) By the Spirit, we become convinced that God the Father loves us. We know that even if a mother would be without tenderness for the child of her womb, our heavenly Father will never stop loving us (see Is 49:15). The Spirit opens our eyes to realize that after the Father has sent the Son to die for love of us, we can be sure that our Father will never forsake us (Rm 8:32). "See what love the Father has bestowed on us in letting us be called children of God! Yet that is what we are" (1 Jn 3:1). We have no more reason to fear. If God the Father "is for us, who can be against us?" (Rm 8:31)
When we receive the Spirit from the Father and the Son, we begin to know and trust the Father and the Son so deeply that we can fearlessly face death, endure sufferings, and live the risen life. Come, Holy Spirit!