There are many other forms of spiritual work, yet not one in itself is all-sufficient; but prayer of the heart, according to St John Klimakos, is pre-eminent and all-embracing, the source of the virtues and catalyst of all goodness. “There is nothing more fearful than the thought of death,” says St Maximos, “or more wonderful than mindfulness of God,” indicating the supremacy of this activity.
But some do not even wish to know that we can attain a state of active grace in this present life, so blinded and weak in faith are they because of their ignorance and obduracy.
~St Gregory of Sinai
Prayerful Life 