I sought the LORD, and he answered me and delivered me from all my fears.
Psalm 34:4
Fear is overwhelming anxiety and worry which immobilizes our spirits into believing that our circumstances are bigger than God’s provision.  The sin of fear fails to trust God: fear declares that God is not adequate to met our daily needs. Fear causes us to freeze in our tracks preventing us from going on with God. The resurrected Jesus can and will overcome our greatest difficulties. He is greater than our fears.
Fearful feelings is not the same thing as the sin of unbelief. One may feel extremely afraid, yet choose to stand on God’s promises. Rather than sink into the pit of despair, we can reach out in faith believing that God will be faithful.  Focusing on the power of the resurrected Christ gives us the confidence and certainty that the things we dread are not bigger than God’s almighty strength and faithful promises.
Fear resides in the heart. Take it physically, if you take a deep breath, you cause your heart to pump the blood faster through your veins, and physical fear goes; and it is the same with the spirit. God expels the old fear by putting in a new Spirit and a new concern. What is that concern? The fear lest we grieve Him.
Oswald Chambers, Biblical Psychology: A Treasure Chest for Christian Counselors (London: Simpkin Marshall, 1996).