Mark 11:24

For this reason I am telling you, whatever things you ask for in prayer (in accordance with God’s will), believe (with confident trust) that you have received them, and they will be given to you. 

Doubt is the enemy and gets in the way of receiving God’s promises. Faith is being fully convinced in what God says and His promises to those who believe. Inspect the internal dialogue: Is it in faith and according to the Word? What we keep before our eyes and in our hearts is what we will believe, whether it is faith or fear.