Quote from : The Way of the Heart: Desert Spirituality and Contemporary Ministry Book

From the heart arise unknowable impulses as well as conscious feelings, moods, and wishes. The heart, too, has its reasons and is the center of perception and understanding. Finally, the heart is the seat of the will: it makes plans and comes to good decisions. Thus the heart is the central and unifying organ of our personal life. Our heart determines our personality, and is therefore not only the place where God dwells but also the place to which Satan directs his fiercest attacks. It is this heart that is the place of prayer. The prayer of the heart is a prayer that directs itself to God from the center of the person and thus affects the whole of our humanness.