John Piper in his challenging book, "Brothers we are not professionals", describes the great dangers inherent in working in Christian ministry. He cites the particular problems of busyness, lack of discipline and interruptions - meaning that one's own spiritual life is gradually destroyed. “Ministry is its own worst enemy. It is not destroyed by the big bad wolf of the world. It destroys itself." How much we need prayer, he argues, for without it the ministry of word dries up. But “activity may continue, but life and power and fruitfulness fade away. Therefore, whatever opposes prayer opposes the whole work of ministry….And what opposes the pastor’s life of prayer more than anything? The ministry.”
Elsewhere, in a biographical article on John Owen, he comments that "one great hindrance to holiness in the ministry of the word is that we are prone to preach and write without pressing into the things we say and making them real to our own souls. Over the years words begin to come easy, and we find we can speak of mysteries without standing in awe; we can speak of purity without feeling pure; we can speak of zeal without spiritual passion; we can speak of God's holiness without trembling; we can speak of sin without sorrow; we can speak of heaven without eagerness. And the result is a terrible hardening of the spiritual life." The act of preaching and the drive of ministry can have a terrible hardening effect on the heart. Ministry can make us more the hypocrite than Christ-like. Piper cites John Owen on the need to keep warming the soul, " A man preacheth that sermon only well unto others which preacheth itself in his own soul. And he that doth not feed on and thrive in the digestion of the food which he provides for others will scarce make it savoury unto them; yea, he knows not but the food he hath provided may be poison, unless he have really tasted of it himself. If the word do not dwell with power in us, it will not pass with power from us."