Spiritual maturity happens over time.  It is a gradual process that requires patience and hardships.  Those who believe that spiritual maturity in Christ is only for a chosen few have not carefully read the Scriptures.  God's plan is for all of his chosen ones to ultimately be conformed into the likeness of Jesus.  Jesus is God's prototype new Man.  Even the old Adam who fell in Gan-Eden will become like Jesus by the power of God for he too was saved by the sacrifice of Jesus.  God uses small things in life to mold us into the likeness of Jesus.