If you saw a grapefruit growing on an apple tree, you would know that something strange was going on. It is not in the nature of an apple tree to produce grapefruits; it produces apples. The new nature that God created in you at the moment of your salvation is a faith nature birthed from a faith God.
When Christians doubt, they are going against the natural process of their new life. The fact that doubt is so commonplace does not make it normal.
Given the reliable and wonderful promises God has provided for us, we should be living in confidence and acting in faith because it is the most natural thing that our born-again spirit can do. Every believer has faith, every believer believes.
“Father, I determine to live by my new nature today. Help me to walk by faith with confidence. I claim the promise of a new creation which You have given to me. I declare that my confidence and trust is in You, and I refuse to submit to the arrows of doubt cast against me by the enemy.”