The "Christians" Who Will Hear "I never knew you"

Imagine the shock people go into when they find out they have cancer and even worse that the the insurance they thought they had is not actually valid and will not take care of their medical bills.  How much more the terror of those who have loved God, prayed to Him and gone to church all their life and when they die, they hear, "I never knew you."  Can you imagine the terror and complete shock in that moment.  WOW!  In 2 Corinthians 15:3, Paul pleads with people who call themselves "Christians" to examine their faith and to test themselves to see whether the Spirit of Christ is really living in them.  There is no doubt in the minds of God fearing preachers and true men and women of God, that the majority of people sitting in churches in America will not make it to heaven, so how can we be for sure that we are truly born again, from heaven's perspective not just our church.