Examine Yourself (2 Corinthians 13:1-9)

When we make a profession of faith we might think that we are in the church and we have arrived at the last step in our Christian walk.  We hear the Apostle Paul exhort us through the Corinthian church to examine ourselves to see if we are in the faith.  Does Paul mean that when people make a profession that they are not in the faith?  Is the Apostle Paul saying that we just randomly loose our faith?  How do we live out this faith in Christ?