The straightforward answer to that question is that being human means being Christ. Our mission, should we chose to accept it, is to grow up into Christ.
Jesus is the last Adam (1 Corinthians 15.45) , and we are human in Christ.
Jesus called himself "Son of Man" meaning, in the Aramaic, "someone like you". Which means we're someone like him! Our humanity is in Christ, and in Christ we are being oned with God.
From this basic premise we can begin to work a Christian Anthropology.
The goal of Orthodox spirituality, the blessedness of the Kingdom of Heaven, is not the vision of the essence, but, above all, a participation in the divine life of the Holy Trinity; the deified state of the co-heirs of the divine nature, gods created after the uncreated God, possessing by grace all that the Holy Trinity possesses by nature.
Vladimir Lossky The Mystical Theology of the Eastern Church Chapter 3
more from Vladimir Lossky....
Christ becomes the sole image appropriate to the common nature of humanity. The Holy Spirit grants to each person created in the image of God the possibility of fulfilling the likeness in the common nature. The one lends His hypostasis to the nature, the other gives His divinity to the persons. Thus, the work of Christ unifies; the work of the Holy Spirit diversifies. Yet, the one is impossible without the other. The unity of nature is realized in persons; and persons can only attain to perfection–become fully personal–within that unity of nature, in ceasing to be ‘individuals’ living for themselves, having their separate individual nature and will. The work of Christ and the work of the Holy Spirit are therefore inseparable. Christ creates the unity of His mystical body through the Holy Spirit; the Holy Spirit communicates Himself to human persons through Christ. Indeed, it is possible to distinguish two communications of the Holy Spirit to the Church: one was effected by the breath of Christ when He appeared to His apostles on the evening of the day of His resurrection (John xx, 19–23); the other by the personal coming of the Holy Spirit on the day of Pentecost (Acts ii, 1–5).