In chapter 12 of his book on Spiritual Mindedness John Owen writes, “Without spiritual affections we cannot be spiritually minded.”
He then tells us why this is so. “By nature our affections, all of them, are depraved and corrupted. Nothing in the whole nature of man, no power or faculty of the soul, is fallen under greater disorder and depravation by the entrance of sin than our affections are. In and by them is the heart wholly gone and turned off from God.”
It gets worse: “[The affections] are , as depraved, the seat and subject of all lusts, both of the flesh and of the spirit; yea, lust or evil concupiscence is nothing but the irregular motion and acting of our affections as depraved, defiled, corrupted, Rom. vii. 8. Hence no one sin can be mortified without a change wrought in the affections.”
That last sentence is particularly insightful. All our efforts to stop sin in ourselves are doomed to fail unless our affections are first changed. Therefore, the key to change is not in self-discipline and will-power (these, to be sure, help, but they can only do so much) but in changing the affections.
The mind is helpless against the affections: “Rebellion against the light of the mind is the very form whereby their corruption acts itself, Job xxxiv. 13. Let the apprehensions of the mind and its notions of good and evil be what they will, [the affections] reject them, and lead the soul in pursuit of their inclinations.”
Then comes this sobering conclusion: “[There] is no greater spiritual judgment than for men to be given up unto themselves and their own evil affections, Rom. 1:26.
I remember a quote from somewhere which says something like this, “We have seen the enemy and the enemy is us.” And this prayer: “From ourselves, O Lord, deliver us!”