We read in the Acts of the Apostles, "And when the day of Pentecost was fully come, they were all with one accord in one place." Thus it came to pass that there was the sound as of rushing wind and a tongue of fire rested on the head of each disciple. Thereby was the Church established through the outpouring of the Holy Spirit, and the Apostles--who had aforetime cowered behind a closed door "for fear of the Jews"--were emboldened to go forth into all the world to preach the Good News of salvation.
The important thing to note here is that the Holy Spirit was given to the ecclesia ('gathering' or 'assembly'), not to individual believers scattered here and there. It is first and foremost to the Church that God reveals Himself, contrary to the Protestant concept so prevalent nowadays that God inspires the individual believer with knowledge of the Truth. Thus, each Christian is considered competent to interpret Scripture according to his personal inspiration, while Holy Tradition (which is God's continuing revelation to the Church through the Holy Spirit) is generally cast aside as irrelevant.
It is, of course, true that we all received the Gift of the Holy Spirit at our Baptism and Chrismation, and that our goal in life (as St. Seraphim of Sarov affirms) is to acquire ever more of the Holy Spirit of God. It is, however, only within the Church, as members of Christ's Body, that we receive this Gift. Certainly no private revelation can ever contradict those truths taught by the Fathers and preserved in the Holy Tradition of the Church. Truly, the Church is the pillar and foundation of the Truth, and our only Ark of Salvation upon the billowing waves of this storm-tossed life.
There truly is but "one Church, one Faith, one Baptism, and one God and Father of us all." Though it may be that we are damned alone, we can only be saved within the communion of the Faith. It is true that a separate tongue of fire rested upon each one present on the day of Pentecost, which testifies that we have all been granted unique gifts and a unique place within the Church. Nevertheless, it is only within the context of the Church that we are enabled to fulfill our true potential as sons and daughters of God.