I suppose you could just ask John Loftus or Bart Erhman, or soon enough, Rob Bell. Ask them what they were thinking as they read the Bible. Or, for example, ask John what event led to him leaving the ministry.
Or you could read 1st and 2nd John.
“So we are lying if we say we have fellowship with God but go on living in spiritual darkness; we are not practising the truth. If we claim we have no sin, we are only fooling ourselves and not living in the truth. If we claim we have not sinned, we are calling God a liar and showing that His word has no place in our hearts. If someone claims, “I know God,” but doesn’t obey God’s commandments, that person is a liar and is not living in the truth.”
Or simply pay attention to the reality that is your life. For example:
Have you lost sight of the gospel in your personal life?
Do you sense a growing disconnect between your private and public life?
Is your day no longer driven by a sense of worship?
Do you feel misunderstood by Christians?
Do Christians seem to cringe at your thoughts, words and behaviours?
Do you find yourself looking for life in places where you once said it couldn't be found?
Are you saying to yourself that following Jesus is no longer a privilege and a joy but is now a burden?
Those who have a healed and forgiven relationship with Jesus will follow a steady road of progress, regardless of bumps and hurdles. Your relationship with God may be hot at times and cold at times but it will never be lukewarm. Those who simply had faith in faith will slowly but surely drift away.
As John said, “Those who leave us were never with us.”
Sad but true.