From a historical/ecclesiological/liturgical perspective, Pentecost, without a doubt, is the Birthday of the Church: Historically, because the Church was founded on this day, ten days after the Ascension of her Lord into Heaven, and on the fiftieth day of His Resurrection from the dead. Ecclesiologically, because simply put, there would be no "church" had there not been Pentecost, the Feast of the Descent of the Holy Spirit, the Promise of the Father, sent by the Son, and, proceeding from the Father "through" (not, "and") the Son. Liturgically, because the annual Weekly and Sunday cycles of Lectionary Readings, are launched with respect to Pentecost (e.g. Twentieth Sunday after Pentecost, or, Wednesday of the Fifteenth Week after Pentecost, and so on).
The historical significance, that of typology and allegory, when compared to the Old Testament, cannot be undermined. In the Old Dispensation, after that the Lord, with a Mighty Hand through Moses His Prophet, had delivered the captive Hebrews from bondage, vis-a-vis the Mosaic Passover, the Giving of the Law was inevitably next, and liturgically in the Hebrew tradition it came to be commemorated as the most sacred event, which occurred not in the Land of Promise, but, in the wilderness of Sinai. Typologically, because the Giving of the Law in the Old Dispensation was a Type, to be fulfilled with the Law of the Spirit, in the New Dispensation. Allegorically, from the Greek "allos" which points to "the other", because the written code, the Law, could not be interpreted without the Spirit.
When reading the account of the Day of Pentecost, in the New Testament, some can be tempted to limit their understanding of the event to what is contained in chapter 2 of the Acts of the Holy Apostles. Lightly interpreted, most associate the event with that of "speaking with tongues" and hence the variant and loose interpretations. The Kontakion of Pentecost reasserts the typological/allegorical element of the Feast:
"When the High One descended, confusing the tongues, He divided the nations. And when He distributed the fiery tongues, He called all into unity. Wherefore, in unison, we glorify the Most Holy Spirit."
It is clearly evident that there is a compare/contrast scheme here: In the Old Dispensation, the Descent of the Spirit upon the Tower of Babylon intended to scatter the Nations into disunity, whereas, in the New Dispensation, the role is reversed, thereby calling all into unity. It is a role-reversal, if you wish, under different circumstances and contexts, in simple terms.
The question in the title begs us to pause for one moment, and ask ourselves: What does Pentecost mean to us? It is a valid question which demands an answer. For those of us baptized Orthodox, the quickest answer that comes to mind is our Orthodox Baptism, pointing to when we were chrismated with Holy Chrism; for converts, the Sacrament of Chrismation. Whether viewed ecclesiologically or personally, we are tempted to point to historical sources: In the case of the Church, it was founded on the First Pentecost; in our case, it was on our Baptism/Chrismation. This is a serious temptation which locks us in the past; it renders our faith static.
But our faith is dynamic, and could not be static. It has to be in order for it to be real, changing our lives daily, and helping us and others as we mature spiritually. We have to hold true the fact that we cannot accomplish anything on our own. Before Pentecost, the Apostles were powerless and cowardly, yet after Pentecost, they were filled with power and courage. Before Pentecost, they were simple fishermen, but after Pentecost they became spiritual orators. Before Pentecost, the Church consisted of merely 120 people, but after the Descent of the Holy Spirit "three thousand souls were added to the Church." Pentecost changed their lives, and it ought to do the same for us.
During the Divine Liturgy, when the faithful are in church, many fail to pay attention to the prayer of the Consecration of the Gifts, uttered by the Celebrant: "Wherefore, O Master, send down Thy Holy Spirit upon us, and upon these gifts here spread forth, and make this Bread the Precious Body of Thy Christ, Amen, and that which is in this Cup the Precious Blood of Thy Christ, Amen, changing them by Thy Holy Spirit, Amen, Amen, Amen." Many fail to see that in this most illustrious moment of the Eucharist, we experience a Pentecost!
The Liturgy of the Faithful (Holy Communion) is preceded by the Liturgy of the Word: We are "fed" the Word before we are fed the Gifts. The two liturgies are inseparable, for together they constitute the Divine Liturgy. Some of the faithful (I have seen it in several parishes) may get upset whenever their Priest requires them to be early in attendance in order to be worthy to receive Holy Communion, but there is no reason to be upset. The Priest, in other words, is instructing the flock that they must be a part of the Liturgy of the Word, not only the Liturgy of the Faithful, therefore, they should not be late. The Disciples were fed the Word, from the Living Word Himself for Three Years, prior to being fed His Body and Blood.
In answer to the main question, I believe that only a prayerful life can lead to an ongoing personal Pentecost in each and every one of us. Even Prayer itself is useless without the Holy Spirit. One of the Matins Prayers reads: "...For we know not how we ought to pray, unless guided by Thy Holy Spirit..." A life of prayer is what invites the Holy Spirit into our lives, in a dynamic fashion. Pentecost need not be limited to a historical event, to two thousand years in the case of the Church, or to our infancy or adulthood, depending, to the time of our Chrismation. It cannot be. We cannot be upright, unless we are led by the Holy Spirit, Who is God. The Koinonikon (Communion Hymn) of Pentecost says: "Thy Good Spirit shall lead me in the land of uprightness" Psalm 142:12.
The sayings of the Holy Fathers are important, yet there is one which always resonates in our hearts and minds, from Saint Seraphim of Sarov: "The true goal of our Christian life consists of acquiring God’s Holy Spirit. Fasting and vigil, prayer, mercy, and every other good deed performed for Christ — are means for acquiring the Holy Spirit of God. Only deeds performed for Christ give us the fruit of the Holy Spirit."
Let us not limit, or reduce, Pentecost to a historical event. Graduations, Weddings, Anniversaries, Birthdays, etc. all of these are historical events. Pentecost should not be as one of these. It should be dynamic, having meaning in our daily lives. It should be, as it is, a "fire", as the Forerunner and Baptist John stated: "I indeed baptize you with water unto repentence, but He who is coming after me is mightier than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and fire" Matthew 3:11. That is why the Great Apostle, in the first document of the New Testament, entreats us: "Do not quench the Spirit" I Thessalonians 5:19, because the Holy Spirit is Fire.
