However, in Romans 8:13, Paul explains that it is by the Spirit that sin is put to death. What does the Spirit do? The Spirit causes us to see sin as filthy and Christ as beautiful:
The third reason why God denies assurance to his most precious ones, is that they may be the more clearly and fully convinced of that exceeding sinfulness and bitterness that is in sin, Jer. 2:19.1 Ah, Lord, says the soul that [is] sighing and mourning under the want of assurance, I see now that sin is not only evil, but the greatest evil in the world, in that it keeps me from an assurance of my interest in thee, who art the greatest good in the world, and from an assurance of that favour of thine that is better than life, and from the light of thy sweet countenance, that is better than corn, and wine, and oil; and from those joys and comforts that can only make a paradise in my soul, Ps. 4:7, 63:3, 4. Ah, Lord! now I find sin not only to be bitter, but to be the very quintessence of bitterness. Ah! no bitterness so bitter as sin, that keeps my soul from that sweet assurance, that is not only the top and crown of mercy, but also the sweetener of all mercy, misery, and glory.2 Oh what unspeakable evil do I now see in that evil that keeps me from the most desirable good! Oh what bitterness do I now find in that which Satan, the world, and my own deluded heart told me I should find sweetness in! Ah, now I find by experience, that to be true, which long since the faithful messengers of the Lord have told me; viz., that sin debaseth the soul of man, that it defiles and pollutes the soul of man, that it renders the soul most unlike to God, who is optimum maximum, the best and greatest, who is omnia super omnia, all, and above all, and renders it most like to Satan, who is a very sea and sink of sin.4 That it hath robbed the soul of the image of God, the holiness of God, the beauty of God, the glory of God, the righteousness of God, and that keeps the soul from wearing this golden chain of assurance.
Thomas Brooks, The Complete Works of Thomas Brooks, Volume 2, “A Serious Discourse Touching a Well-Grounded Assurance”, ed. Alexander Balloch Grosart, (Edinburgh; London; Dublin: James Nichol; James Nisbet and Co.; G. Herbert, 1866), 332.
Thus, holiness is the nature outflow of desire for Christ. Christ is desired above all rivals.