The world is at this day full of poor withering professors. How few are there that walk in any beauty or glory! how barren, how useless are they, for the most part! Amongst the many reasons that may be assigned of this sad estate, it may justly be feared that this is none of the least effectual,—many men harbour spirit-devouring lusts in their bosoms, that lie as worms at the root of their obedience, and corrode and weaken it day by day. All graces, all the ways and means whereby any graces may be exercised and improved, are prejudiced by this means; and as to any success, God blasts such men’s undertakings.
– John Owen –
from The Mortification of Sin in Believers, volume 6 of Works, page 56