And they that are Christ’s have crucified the flesh with the affections and lusts.
Galatians 5:24 (KJV)

By flesh we are here to understand carnal lust, the workings and motions of corrupt nature; and by the affections we are to understand, not the natural, but the inordinate affections; for Christ doth not abolish and destroy, but correct and regulate the affections of those that are in Him.

And by crucifying the flesh, we are not to understand the total extinction or perfect subduing of corrupt nature, but only the deposing of corruption from its regency and dominion in the soul; its dominion is taken away, though its life be prolonged for a season; but yet, as death surely, though slowly, follows crucifixion, (the life of crucified persons gradually departing from them, with their blood) it is just so in the mortification of sin; and therefore what the apostle in this place calls crucifying, he calls in Romans 8:13 mortifying. “If ye, through the Spirit, do mortify,” if ye put to death the deeds of the body. But he chooses, in this place, to call it crucifying, to show not only the conformity there is between the death of Christ and the death of sin—in respect of shame, pain, and lingering slowness—but to denote also the principal means and instruments of mortification, that is the death, or cross of Jesus Christ, in the virtue whereof believers do mortify the corruptions of their flesh.

The great arguments and persuasives to mortification are drawn from the sufferings of Christ for sin. In a word, he doth not say, They that believe Christ was crucified for sin, are Christ’s; but they, and they only, are His, who feel as well as profess the power and efficacy of the sufferings of Christ, in the mortification and subduing of their lusts and sinful affections.

—John Flavel
Adapted from The Whole Works of the Reverend John Flavel, 2:369.