Grade
4: Prayer of Simplicity

It is simply the prayer of acquired recollection, a simple love or gaze on some divine object, whether on God Himself, His nature, the Holy Eucharist, some Christian truth or mystery. The former reasoning and affection have now been transformed into a simple loving attention on the divine. The prayer is the last grade of ascetical prayer, meaning that the soul is able to attain to this prayer by its own effort with the help of ordinary grace. There is no particular method for this prayer. All it takes is a simple loving gaze and attention admid a great deal of sacred space and quietude. However, it takes a certain intensity of God's grace or Energy to do so, i.e., the intensity which builds up through the former three grades of prayer. (cf. Spiritual Theology, pp.327-328)
All souls need this simple sacred quietude regularly for sufficient nourishment, recollection, concentration and rest in the Lord. Otherwise, the soul would increasingly or slowly lose its centre of gravity and suffer untold damage in the midst of endless commitments, noises, distractions and disturbances. The soul would even lose its health and sanity, unable to make simple discernment and right judgment. The devil, concentration camps and even modern life itself certainly know how to disturb and deteriorate a soul of God who by nature needs such daily prayer of simplicity.
God is always willing and eager to grant us this prayer, as we read: "The Lord is my shepherd, I shall not want. He makes me lie down in green pastures; he leads me beside still waters; he restores my soul. He leads me in right paths for his name's sake." (Ps 23:1-3) Hence, each time when we go to prayer, we should cooperate with the Lord and generously give ourselves sufficient time also for this prayer. This is when God's love, joy, peace, wisdom, discernment, rest, and anointing, etc., would begin to slowly permeate and even overflow our soul. This is when we begin to experience the following more deeply: "Even I walk through the darkest valley, I fear no evil: for you are with me; your rod and your staff - they comfort me. You prepare a table before me in the presence of my enemies; you anoint my head with oil; my cup overflows. Surely goodness and mercy shall follow me all the days of my life." (Ps 23:4-6a)
We may begin to want to spend a lot more time before the Lord. "And I shall dwell in the house of the Lord my whole life long." (Ps 23:6b) Yet, in varying degrees, we may find ourselves continuously hindered by various unknown forces. Prayer is indeed a daily battle. How deep we pray can be defined by how deep we can tap into God's Energies, the unshakable foundation of all creation everywhere. Between God and us, there are various types of unholy and unwanted energies disorienting us from God's holy presence. However, the Lord is always our good Shepherd who enjoys blessing us. With our patient cooperation, God will guide us through.
Fr. Aumann cautions us as follows: "During the practice of the prayer of simplicity, the soul should strive to preserve the loving attention that is fixed on God, but without forcing itself. It must avoid distractions and slothfulness, but if it exerts too much effort it will destroy the simplicity of the prayer. Psychologically it is difficult for us to remain attentive over a long period of time, and therefore we should not expect, especially in the beginning, to be able to practice the prayer of simplicity for long periods of time. As soon as the loving attention begins to waver, we should turn to the use of affective prayer or simple meditation. All must be done gently and without violence. Nor should the soul be upset if periods of dryness occur. The prayer of simplicity is not always sweet and consoling type of prayer; it is also a transition from ascetical to mystical prayer, and therefore the soul may experience the aridity that normally accompanies transitional states." (Ibid., p.328)
For further inspiration, chick here.