Christ has conquered all in his own person first, and he is ‘over all, God blessed for ever’ (Rom. 9:5), and therefore over sin, death, hell, Satan and the world. And, as he has overcome them in himself, so he overcomes them in our hearts and consciences. We commonly say that conscience makes a man kingly or contemptible, because it is planted in us to judge for God, either with us or against us. Now if natural conscience be so forcible, what will it be when, besides its own light, it has the light of divine truth put into it? It will undoubtedly prevail, either to make us hold up our heads with boldness, or abase us beneath ourselves. If it subjects itself, by grace, to Christ’s truth, then it boldly faces death, hell, judgment and all spiritual enemies, because then Christ sets up his kingdom in the conscience and makes it a kind of paradise.
Excerpt from Grace Shall Reign by Richard Sibbes: