Michael Horton writes on keeping your mind fixed on the Gospel:
The gospel is greater than we ever imagined, and the judgment is severe for those who reject the realities it brings into our lives.
An illustration will help us to bring these threads together. Imagine a new sailboat with all of the latest gadgets. Equipped with satellite technology, the sailboat can plot the course to your destination. It can even signal alarm when you veer from its coordinates. Relying on the impressive gear, you venture out into the open waters under full sail until eventually the winds die down and you come to a dead calm. The radio warns that a squall is suddenly approaching out of the east. A number of fellow sailors offer advice on their radios, but despite all of the information offered by the guidance system itself and the helpful advice of colleagues, you realize that you cannot return to safety without any wind. So there you sit, with all of your finest technology, unable to move toward the harbor.
The Christian life is often like this. We glide out of our harbor under full sail, thrilled with delight in knowing our sins are forgiven and that we are right with God. A new love for our Redeemer fills us with gratitude, and we are eager to follow the course he has set for us in his Word. Yet as we pass into the open seas, we encounter spiritual stress. God’s law, we find, provides the direction but not the power, and a panoply of spiritual technologies are available to substitute. We think that by reading this book or going to that conference or following this plan for spiritual victory or these steps for overcoming sin in our life, we can get the boat going in the right direction again.
These guides are usually neither law (i.e., God’s directives) nor gospel (i.e., God’s promises and acts in Christ), but helpful advice from fellow sailors. In a sense, the advice they offer is more law than gospel, since it imposes expectations and demands as conditions for success. Yet the more advice you get, the deeper your sense that you are simply dead in the water spiritually. Exhausted, you either give up and promise never to sail again or you realize that what you really need is a fresh gust of wind in your sails. That wind is always Christ in his saving office. What you really need is to be told all over again about who God is and what he has done to save you, and about the new world that awaits you because of his faithfulness to unfaithful sailors. This alone will fill your sails so that you can get safely back to the harbor when the gales blow hard.
Our whole life as Christians is a process of sailing confidently into open seas, dying down in exhaustion, and having our sails filled again with God’s precious promises. We are never at any moment simply under full sail or dead in the water, but move back and forth throughout the Christian life. This is the movement that we find in Romans 6-8, from the triumphant indicative (Rom. 6:1-11), to the moral imperatives (6:12-14), back to the indicatives (6:15-7:6), to the exhausting struggle with sin (7:7-24), back again to the triumphant indicative, “Thanks be to God through Jesus Christ our Lord!” (7:25) and the future hope awaiting us for which even now we have the Spirit as a down payment (8:1-39).
Thus the crucial point in all of this is that even in its third use (guiding rather than condemning), the law can do only what the law does. We must not think that the law drives us to Christ in the beginning (second use) and then Christ drives us back to the law for our acceptance before God in sanctification (third use). Rather, the law continues to provide us with the soundest guidance available, but apart from Christ and the indicative announcement of what he has done for us and in us, it can only lead us to either despair or self-righteousness. No less than when we first believed, we must always attribute to the gospel the power that fills our sails with gratitude, and to the law the proper course that such gratitude takes. At the beginning, in the middle, and at the end, the gospel “is the power of God for salvation to everyone who believes” (Rom. 1:16).
(From: Michael Horton, God of Promise, Introducing Covenant Theology (Grand Rapids: Baker, 2006), 193-194.)