Conferences of St. John Cassian: Conference One Part I - Purity of Heart

Therefore, we must follow completely anything that can bring us to this objective, to this purity of heart, and anything which pulls us away from it must be avoided as being dangerous and damaging.

With this as our continuous aim, all our acts and thoughts are fully turned toward its achievement, and if it were not ever firmly before our eyes all our efforts would be empty, hesitant, futile, and wasted, and all the thoughts within us would be varied and at loggerheads with one another. For a mind which lacks an abiding sense of direction veers hither and yon by the hour, and by the minute is a prey to outside influences and is endlessly the prisoner of whatever strikes it first