From The God Who is There, by D.A. Carson:
God's Spirit transforms us by bringing us back to the cross so that all of our morality is first and foremost a function of gratitude to God for what Christ has already done. If you begin to see just how much you were forgiven by what Christ did on the cross, how on earth can you possibly nurture bitterness toward others? If you see what is still in store for the future, that you have already received in part by the down payment of the Sprit who strengthens your moral resolve and gives you vistas of a new heaven and a new earth, how can you possibly be locked into the agonizing, painful, limited concerns of a world that will pass away? You are destined for eternity with God Almighty. That changes everything. When there is a moral slide in the church or in the broader world, what we must have more of is an accurate, thick, rich understanding of the gospel, for it transforms us.