James 1:6-7 But he must ask in faith without any doubting, for the one who doubts is like the surf of the sea, driven and tossed by the wind. For that man ought not to expect that he will receive anything from the Lord
What you were "believing" for in prayer won't come to you, even though you believed it with your whole heart "during the prayer" because "you stopped believing" that you would receive it.
This phenomenon has made so many people believe that their prayers are just plain ineffective.
So many people believe they will receive what they are asking for "while they are praying for it", only to find themselves later doubting that their prayer will be answered.
It starts with small thoughts of "what if's" and "maybe it won't happen." The doubt starts because the enemy comes and steels "that belief" by sowing seeds of doubt and unbelief into their thoughts.
You have to stay in line with the blessing that is coming to you.
You do this by "standing in your belief". You stand in belief the way Jesus stood in belief when he spoke to the enemy in the desert. When you stand in belief you are staying in line with the blessing that God has for you.
If you get out of that line (by unbelief, fear, or doubt) the enemy can steel that blessing because you were not there to receive it.
What is the enemy stealing? Your blessing.
What is he killing? Your dreams.
What is he destroying? Your destiny.
It is like an interception in football. The quarterback (God) throws the ball (the blessing). He intends for the receiver (you) to catch it, but if you get out of line with the direction the ball is going in (the blessing), and you go in another direction (unbelief, fear, doubt), then a player on the other team (the enemy) is free to "intercept" (steel) the ball (your blessing). Once he intercepts the ball (your blessing) he is free to run in the other direction away from you, with the ball (your blessing).
So the goal is to keep ourselves "in line" with God and His word by "prayer and belief," so we can stay "in line" with the blessings God has for us. Remember, the Lord said that whatever you ask for in prayer, you will receive, "if you believe", but that "belief" is not only during the prayer. You must also "believe" and "stand in that belief" until you "receive" what you prayed for. When you start doubting, you start going in another direction away from the blessing the Lord has for you.
So how do you stand in your belief? One of the best ways I have found is by speaking scripture out loud when the enemy tries to sow those seeds of doubt.