John of the Cross and the Importance of Appetite

I read this passage from The Ascent of Mount Carmel by John of the Cross this morning:

The ignorance of some is extremely lamentable; they burden themselves with extraordinary penances and many other exercises, thinking these are sufficient to attain union with divine Wisdom. But such practices are insufficient if these souls do not diligently strive to deny their appetites. If they would attempt to devote only half of that energy to the renunciation of their desires, they would profit more in a month than in years with all these other exercises. As the tilling of soil is necessary for its fruitfulness—untilled soil produces only weeds—,prettification of the appetites is necessary for one's spiritual fruitfulness. I venture to say that without this mortification all that is done for the sake of advancement in perfection and in knowledge of God and of oneself is no more profitable than seed sown on uncultivated ground. Accordingly, darkness and coarseness will always be with a soul until its appetites are extinguished. The appetites are like a cataract on the eye or specks of dust in it; until removed they obstruct vision. (I.8.4)

It almost struck me as ironic: after all, reading John is for me now, a spiritual exercise! But he himself calls me to think about the things within me that actually need changing, particularly the restrain of my physical appetites. My devotional life should be connected to the rest of my life; my prayer should grow from and flow back into the actual living of my life,  in the awareness of how the Lord is changing me, growing and purifying my heart, words, thoughts, and actions.  Prayer cannot be only an isolated spiritual exercise, but must be accompanied by a willingness to be thoroughly changed by the Lord.