It is well understood, I suppose, that the Will acts, if it acts at all, in accordance either with natural and interested motives on the one hand, or of moral motives on the other. In a mind, that is not the subject of any degree of alienated action, and which, therefore, in the ordinary sense of the terms, may properly be called a sound mind, the moral sense will always act right and act effectively, and will always furnish a powerful motive to the Will, unless it is perplexed and weakened in its action, (which, however, is very likely to be the case in the natural man,) by the influence of unsanctified desires.
If, therefore, the desires are sanctified, and the perplexing and disordering influence from that source is taken away, the feelings of desire and the sentiment of justice will combine their action in the same direction, and the action of the Will cannot be otherwise than holy. To possess holy desires, therefore, in their various modifications, or what is the same thing, to possess, as we sometimes express it, a holy HEART, is necessarily to possess a holy WILL. There is no reason, under such circumstances, why the will should not act right. And a right will is a holy will. To secure such a consummation — the appetites subdued, the propensities regulated, the affections sanctified, the will just in its action, and consequently united with the will of God — to secure a result so immensely important in itself and its relations, how devoutly should we pray! How constantly and ardently should we labor!
"Create, O God, my powers anew,
Make my whole heart sincere and true;
Oh, cast me not in wrath away,
Nor let thy soul-enlivening ray
Still cease to shine."
— edited from The Interior or Hidden Life (1844) Part 2, Chapter 9.