The work of prayer belongs to the angels, and is, therefore, the special concern of the Church. Every other work, i.e., charity, nursing the brethren, visiting the sick, caring for prisoners, releasing captives, and other similar things, is done by the brethren in love and offered by them to God. Similarly, poverty, fasting, sleeping on the ground, prostrations, vigils, etc., are good and like a sacrifice to God, because they aim to subdue and humble the body so that we may be purified and approach God and become friends of God -- yet these things do not present us directly to God, whereas prayer does so and unites us with Him. A person praying acts towards God like a friend -- conversing, confiding, requesting -- and through this becomes one with our Maker Himself.
St. Symeon of Thessalonica