To be attentive and watch over oneself, according to the frequent recommendation of the Fathers, means generally to be concerned with oneself–that is, with one’s spiritual being and destiny–rather than with external things. This means especially to endeavor to know and recognize one’s spiritual illnesses, which knowledge is the condition for healing. St Basil says:
“In all things you must strive to know the status and illnesses of your soul. For many have dangerous infirmities, of which they are not aware…”
More generally, this means being attentive to one’s whole being, keeping watch at once over one’s body and soul, monitoring one’s external behavior in order to avoid evil acts, and guarding one’s inner life in order to avoid wicked thoughts.
~Dr Jean-Claude Larchet (Therapy of Spiritual Illnesses vol.2 p.239)
Prayerful Life 