“Most men love to hear of the doctrine of grace, of the pardon of sin, of free love, and suppose they find food therein; however, it is evident that they grow and thrive in the life and notion of them. But to be breaking up the fallow ground of their hearts, to be inquiring after the weeds and briars that grow in them, they delight not so much, though this be no less necessary than the other. This path is not so beaten as that of grace, nor so trod in, though it be the only way to come to a true knowledge of grace itself. It may be some, who are wise and grown in other truths, may yet be so little skilled in searching their own hearts, that they may be slow in the perception and understanding of these things. But this sloth and neglect is to be shaken off, if we have any regard unto our own souls. It is more than probable that many a false hypocrite, who have deceived themselves as well as others, because they thought the doctrine of the gospel pleased them, and therefore supposed they believed it, might be delivered from their soul-ruining deceits if they would diligently apply themselves unto this search of their own hearts. Or, would other professors walk with so much boldness and security as some do if they considered aright what a deadly watchful enemy they continually carry about with them and in them? Would they so much indulge as they do carnal joys and pleasures, or pursue their perishing affairs with so much delight and greediness as they do? It were to be wished that we would all apply our hearts more to this work, even to come to a true understanding of the nature, power, and subtlety of this our adversary [sin within us], that our souls may be humbled; and that—

In walking with God. His delight is with the humble and contrite ones [Isa. 57:15], those that tremble at his word [Isa. 66:2], the mourners in Zion [Isa. 61:3]; and such are we only when we have a due sense of our own vile condition. This will beget reverence of God, a sense of our distance from him, admiration of his grace and condescension [in Christ], a due valuation of mercy [in the cross], far above those light, verbal, airy attainments, that some have boasted of.”

Overcoming Sin and Temptation – The Power and Efficacy of Indwelling Sin (PDF), John Owen, pg. 282-283