Thus the crucial Role the Spirit plays in Pauline theology, that is, in his and his churches experience of God’s saving grace. For Paul, the “Love of God” is no mere abstraction. God’s love, the most essential reality about his character and the absolute predicate of our existence, has been demonstrated historically in its most lavish and expansive expression through Christ’s death for his enemies (v 6-8, thus the basis for “peace with God” and “access” to his gracious presence). But neither is such love merely and objective historical event. God’s love played out to the full in Christ, is an experienced reality in the “heart” of the believer by the presence of the Spirit. This is what the Spirit has so richly “shed abroad in our hearts”. If one is not overtaken by God himself at this one crucial point, then all else is lost, and one is without peace, grovelling before God, living with little real hope, and thus experiencing present sufferings as a cause for complaint and despair rather than for “boasting”.
From the book "God's Empowering Presence"