 If you are not sure of who God says you are and what the promises are, it is easy to allow doubt to enter into your thoughts. Jesus knew and he answered with the written word. When you find yourself not believing who you are in God or who God says you are, you could find yourself wanting the lack filled more than you want God. Doesn't mean you're not a Christian. It means you don't truly believe God will fill the lack or meet your need.