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