St. John Climacus was asked if there are reliable signs by which it's possible to know whether a soul is drawing near to God or moving away from Him. After all, regarding ordinary things there are clear signs as to whether they're good or not. When, for instance, cabbage, meat or fish begins to rot, it's easy to notice it, since the rotting object begins to give off a foul odor, the color and taste change, and its external appearance witnesses to its deterioration. Well, and what about the soul? After all, it's bodiless and can't give off a bad smell or change its appearance. To this question the Holy Father replies, 'A sure sign of the deadening of the soul is the avoidance of church services.'
Of the teachings and proclamations preserved in the Church, some we possess from written teaching, while others we have received in secret from the Tradition of the Apostles; these both have the same validity [ie. authority] for true religion. And no one will deny these points, at least if he is even moderately experienced in Church [matters].
Sacred Tradition is the very Church; without the Sacred Tradition the Church does not exist. Those who deny the Sacred Tradition deny the Church and the preaching of the Apostles. Before the writing of the Holy Scriptures, that is, of the sacred texts of the Gospels, the Acts and the Epistles of the Apostles, and before they were spread to the churches of the world, the Church was based on Sacred Tradition... The holy texts are in relation to Sacred Tradition what the part is to the whole.
They (namely the Apostles) have not handed down everything in writing, but have also delivered many things in unwritten form. The former and the latter are equally trustworthy, and so we also consider the [unwritten] Tradition of the Church to be trustworthy. Is it Tradition? Seek no further.
The Church Fathers regard Sacred Tradition as the safe guide in the interpretation of Holy Scripture and absolutely necessary for understanding the truths contained in the Holy Scripture. The Church received many traditions from the Apostles... The constitution of the church services, especially of the Divine Liturgy, the holy Mysteria themselves and the manner of performing them, certain prayers and other institutions of the Church go back to the Sacred Tradition of the Apostles.