How, then, should the person worthy of Christ’s great name behave? What can he do except to always discern his thoughts, words and deeds, and to see whether or not they are of Christ or are alien to him? Much skill is needed here for discernment. Anything effected, thought or said through passion has no association with Christ but bears the adversary’s mark; smearing the soul’s pearl with passion as if with mud, it corrupts the precious stone’s brightness. But a state free from every passion looks to the author of detachment, Christ. He who draws to himself thoughts as from a pure, incorruptible fountain will resemble the prototype as water drawn into a jar resembles water gushing from a fountain.
–Saint Gregory of Nyssa (c. 335 – c. 395)