Both extremes are deadly. However, Dom Chautaurd does not devote significant space in his work on the subject. He merely references quietism in passing, an understandable action as the heresy of good works is more apt to abuse in the Church. As a result, we pull the following excerpt from New Advent:
Quietism (Latin quies, quietus, passivity) in the broadest sense is the doctrine which declares that man's highest perfection consists in a sort of psychical self-annihilation and a consequent absorption of the soul into the Divine Essence even during the present life. In the state of "quietude" the mind is wholly inactive; it no longer thinks or wills on its own account, but remains passive while God acts within it. Quietism is thus generally speaking a sort of false or exaggerated mysticism, which under the guise of the loftiest spirituality contains 4 erroneous notions which, if consistently followed, would prove fatal to morality. It is fostered by Pantheism and similar theories, and it involves peculiar notions concerning the Divine cooperation in human acts. In a narrower sense Quietism designates the mystical element in the teaching of various sects which have sprung up within the Church, only to be cast out as heretical. … All these varieties of Quietism insist with more or less emphasis on interior passivity as the essential condition of perfection; and all have been proscribed in very explicit terms by the Church.Source: http://www.newadvent.org/cathen/12608c.htm
In the simplest terms, we can describe quietism as "false piety" or even "ostentatious piety."
Friends, are we guilty of quietism?
If we are, it is not too late to emerge out of this heresy.