For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father. The Spirit itself beareth witness with our spirit, that we are the children of God: And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together.
Romans 8:15-17
God does not just place us into His family when we accept Christ as Savior, He also gives us evidence and proof of that new relationship in the person of the Holy Spirit. Every Christian knows moments of closeness and warmth when we feel very much a child of God. But every Christian also knows moments when we feel abandoned and alone. Though that is never the case, it is easy for us to feel that way in moments of difficulty and trial. Even David, the man after God's heart, had times when he felt like God was sleeping rather than helping him as He should. “Stir up thyself, and awake to my judgment, even unto my cause, my God and my Lord” (Psalm 35:23).
Part of the work of the Holy Spirit in our lives is to provide reassurance and certainty of God's presence with us and His unfailing love for us. He gives us the confidence to cry out for help like an earthly child cries out to his father. That is why it is so vital that we make sure we are not doing something to hinder His work by the way in which we are living. Paul wrote, “And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption” (Ephesians 4:30). The Holy Spirit never leaves a Christian, but we can live in such a way that His voice is drowned out and we lose the assurance and confidence that comes from close fellowship with Him. We need that relationship, and we must take care not to do anything to hinder the Holy Spirit's work in our lives.