Saint Hesychius writes,
Sobriety is the continual situating of the thought at the doors of the heart, so that it sees the thoughts creeping up and understands what form the demons are attempting to inscribe and establish in the mind, so as to entice it through the imagination.Often we refer to this as self discipline. It is a level of spiritual maturity where we are aways aware of our thoughts. This awareness is also called watchfulness. It is where we are always watching for those thoughts that will enter into our minds and stimulate desires that lead us away from the teachings of Jesus Christ.
How do we develop this virtue? If we only follow the Orthodox Way of LIfe taught by the Church we will be lead on a path where we become watchful and have sobriety. This involves daily prayer, practice of the Jesus Prayer, participating in the weekly fast on Wednesdays and Fridays and the other fasting periods specified by the Church. It involves our regular attendance to the Divine Liturgies and participating with proper preparation in Holy Communion and Holy Confession. It also means we will read the Scripture each day. This is an easy discipline that trains our mind, builds self-discipline, and subjects our self-will to the will of God.
I was talking with a young family yesterday and they were describing how a priest who came into their parish was firm in asking his parishioners to follow these practices. There were many in the Church who rebelled and caused him difficulty but they began to follow what he taught them. This lead them to a higher quality of life and one they found to be much "easier" than trying to make up their own approach to their Orthodox Faith. Their teen age children matured and developed responsibility and the younger ones became curios about the teachings of the church asking questions and seeking information on their own. The found the discipline to always eat their meals as a family and to function as an integral family unit. Their lives changed and their love for God increased.
Sobriety is the the result of a very simple act and choice. It involves simply choosing to follow the teachings of the Church about our daily way of life. This simple act will give greater meaning to the crazy world we live in, greater capacity to discern what is right and wrong, a inner quietness and strength to exercise our self-will in conjunction with the teachings of Jesus.
Saint Theophan advises,
I am pointing you directly to the path so that you do not wander all over the place. Be more diligent in your undertaking and you will soon see success. However, you must labor with all your might, because without labor there will be nothing.
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Reference: The Spiritual Life, p 251-252