Romans 4:20

But he did not doubt or waver in unbelief concerning the promise of God, be he grew strong and empowered by faith, giving glory to God. 

Fear is faith in the opposite direction.  Fear believes more in the circumstance than the ability of God to change the circumstance.  Faith in God and His promises are the powerhouse to our lives.  Faith cannot operate when we have fear in our lives about anything.  The stronger our knowledge of the promises of God, the less fear will have a chance.