And I will ask the Father, and He will give you another Advocate to be with you forever— the Spirit of truth. The world cannot receive Him, because it neither sees Him nor knows Him. But you do know Him, for He abides with you and will be in you. — JOHN14:16,17

Jesus promised to ask the Father, who would give another Helper to be with us forever — the Spirit of truth. The Spirit isn't a vague force; He's the personal presence of God dwelling in you. He bears witness that you're a child of God. He helps you pray. He pours God's love into your heart.