There are many different ways to look at this sort of question. St. Anthony counseled that we are to control our eyes, our mouths, and our stomachs, and that is one answer. The canonical rules may specify a number of councils to hold to (or not, depending on whose canons we're talking about ), and that's another answer, insofar as holding to the faith of the Church is concerned. I will say I am a firm believer in what you may call 'collective salvation', in the sense that I've heard EO put it that we are "saved together", yet "damned alone".
With that in mind, I observe as the faith of the Church the following, from the Agpeya:
One is God the Father of everyone.
One is His Son, Jesus Christ the Word, Who took flesh and died; and rose from the dead on the third day, and raised us with Him.
One is the Holy Spirit, the Comforter, one in His Hypostasis, proceeding from the Father, purifying the whole creation, and teaching us to worship the Holy Trinity, one in divinity and one in essence. We praise Him and bless Him forever. Amen.
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This has all the theological necessities (the oneness of God, Trinitarian monotheism, the direct guidance and teaching of the Holy Spirit, etc.), such that if one holds to it they cannot be led astray into other theologies or religions.
The question of what we are to do...well, I would think the answer to that is more varied. Consider the fourth chapter of our father and master St. Paul's epistle to the Ephesians, where he observes the following (verses 11-16):
And He Himself gave some to be apostles, some prophets, some evangelists, and some pastors and teachers, for the equipping of the saints for the work of ministry, for the edifying of the body of Christ, till we all come to the unity of the faith and of the knowledge of the Son of God, to a perfect man, to the measure of the stature of the fullness of Christ; that we should no longer be children, tossed to and fro and carried about with every wind of doctrine, by the trickery of men, in the cunning craftiness of deceitful plotting, but, speaking the truth in love, may grow up in all things into Him who is the head--Christ-- from whom the whole body, joined and knit together by what every joint supplies, according to the effective working by which every part does its share, causes growth of the body for the edifying of itself in love.
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So God gives to each one according to His will for us, till we all come to the unity of the faith and the knowledge of the Son of God. This we have already in the Orthodox Church (as surely Catholics and others would say of their own churches), and also more generally with all Christians who confess the holy faith of Nicaea and Constantinople as outlined in the Orthodox creed given by the Holy Spirit to our fathers there.
This is the "saved together" aspect, that we should all confess the same truth of Him Who is Truth. As to the "damned alone" aspect, there is likewise -- without leaving the first part undone -- a real watchfulness required so as to be in constant repentance and supplication. I've been wrong lately in my specific attributions, so I will just that it was one of the desert fathers who said that if he could see all of his sins, there would not be enough monks even in all the deserts of Egypt to cry over them. I believe that is the reality for all of us, each in our own way having consistently fallen short of the glory of God. Here again, the Agpeya provides a prayer in the litanies for the Compline (retiring hour) that expresses things much better than I ever could:
Behold, I am about to stand before the Just Judge terrified and trembling because of my many sins. For a life spent in pleasures deserves condemnation. But repent, O my soul, so long as you dwell on this earth, for inside the grave, dust does not praise. And among the dead, no one remembers, neither in Hades, does anyone give thanks. Therefore arise from the slumber of laziness, and entreat the Savior, repenting and saying, “God, have mercy on me and save me.”
(Glory be to the Father, and to the Son, and to the Holy Spirit +)
If life were everlasting, and this world ever-existing, you would have an excuse, O my soul. But if your wicked deeds and ugly evils were exposed before the Just Judge, what answer would you give while you are lying on the bed of sins, negligent in disciplining the flesh!? O Christ our God, before Your awesome seat of judgement I am terrified, and before Your council of judgement I submit, and from the Light of Your divine radiance I tremble, I, the wretched and defiled, who lies on my bed, negligent in my life. But I take example of the Publican, beating my chest and saying, “O God, forgive me and have mercy on me, a sinner.”
(Now and forever and unto the ages of ages. Amen.)
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To say such prayers every day and all days in complete sincerity, engaging all of your senses by it and thus bringing the body under the control of the soul that is sincerely supplicating God, is the way that we have individually been given. (Though we do pray the Agpeya collectively in church, as part of the raising of the incense.) The same is the thought behind rigorous fasting, abstinence, and all other disciplines we keep to, and why fasting for instance may be modified according to individual circumstances, in consultation with your spiritual father. Your way is yours just as everyone else's is everyone else's, but we are all striving towards salvation in and through Jesus Christ, Who rose from the dead and will raise us with Him. We look for the resurrection of the dead, and the life of the age to come.
