It is absolutely necessary to shun as the most pernicious of vices the reflex action of the mind, the tendency to come back on ourselves.  This evil is very frequent among moderns who are born with a taste for analysis and psychological curiosity.  If we look at ourselves instead of looking at God, if we tighten our heart in order to scrutinise the state of our soul and take stock of our petty progress, if we leave our prayer in order to find out if it is good, or abandon our “quietude to see if it is really quiet,” as S. Francis de Sales says (Amour de Dieu, VI, 10), agreeing with the descriptions of spiritual writers we lose the whole fruit of our spiritual life, we wander disquieted instead of entering into peace, we take the risk of numberless illusions. (26)

Jacques Maritain | Prayer and Intelligence