At the Last Supper, when Philip asked Jesus to show them (the disciples) the Father, Jesus responded, "Have I been with you for so long a time and you still do not know me, Philip? Whoever has seen me has seen the Father. How can you say, 'Show us the Father'?"
This makes me think that we could be a follower of Jesus for a long time, hear him preached every Sunday at church, read many books about him, participate in parish activities, and still do not know him or the Father. To avoid this pitfall, seek total union with the Lord.