The manifestation of thoughts (ie. revealing our thoughts to make known our inner state) in particular allows one to avoid the sins brought about by hidden thoughts. St Theodore the Studite asks: “Whence does unreasonable activity…come among you? Is it not because you do not reveal yourselves, but hide your evil thoughts?” He notes further: “The origin and root of the sins that we commit is a wicked thought.”
The revelation of thoughts also allows one to prevent the strengthening of existing passions or the forming of new passions, produced when they are given free reign to repeat themselves. Finally, this revelation allows one to avoid having thoughts in the soul that destroy and gnaw away at it, and which in any case might have multiple pathological effects on the inner life precisely because of their hidden character.
Unrevealed thoughts continue to live in the soul, often silently and imperceptibly; they anchor themselves within it, develop there, and gradually poison it. In the end, they take the soul into captivity, from which escape will be all the more difficult since the soul will have refrained for a long time from reacting, and will have been slow to manifest its thoughts. For this reason St John Cassian speaks of “the despotism of hidden thoughts” and “the frightful dominion that they exercise as long as they are concealed.”
~Dr Jean-Claude Larchet (Therapy of Spiritual Illnesses vol.2 p.217)
Prayerful Life 