Please click through and read the whole piece. It is well worth 10 minutes.
This is important. Our union with Christ is dependent upon the Spirit — not our will to believe, though the Spirit fuels our faith; not our intellect, though the Spirit gives light; not our affections, though the Spirit makes us feel; not our obedience, though the Spirit produces fruit. The Spirit himself is the bond of our union, which means, because the Spirit is God, the bond of our relationship with God is God himself. And that means there’s no going back.
This bond does not expire or dissolve. This is what the Spirit does and has always done. Before the foundation of the world, the Spirit was the personal bond of glorious love between the Father and the Son. And now, the Spirit is that love in us (John 17:26; Romans 5:5). He has brought us into an inseparable union — one that is as secure as the Father’s love for the Son, as sure as God’s love is for himself.