John of the Cross (1542-1591) wrote in Dark Night of the Soul regarding the seven sins of the spiritual life. After addressing pride, he moves on to greed.
Many of these beginners will also begin to have spiritual greed, the second capital sin. They will become discontented with what God gives them because they do not experience the consolation they think they deserve. They begin reading many books and performing many acts of piety in an attempt to gain more and more spiritual consolation.
Their hearts grow attached to the feelings they get from their devotional life. They focus on the affect, and not on the substance of devotion. Quite often these souls will attach themselves to particular religious objects or holy places and begin to value visible things too highly.
But those who are on the right path will set their eyes on God and not on these outward things nor on their inner experiences. They will enter the dark night of the soul and find all these things removed. They will have all the pleasure taken away so that the soul may be purified. For a soul will never grow until it is able to let go of the tight grasp it has on God.
(Cited in Devotional Classics, ed. Richard Foster, pp. 34-35)