Don't let others.

I Samuel 23:2 Therefore David inquired of the LORD, saying, Shall I go and smite these Philistines? And the LORD said unto David, Go and Smite the Philistines, and save Keilah. 3. And David's men said unto him, Behold we be afraid here in Judah: how much more then if we come to Keilah against the armies of the Philistines? 4. Then David inquired of the LORD yet again. And the LORD answered him and said, Arise, go down to Keilah: for I will deliver the Philistines into thine hand.
How many times in our lives have we asked God for something. God promised it but we let others cast doubt on what we know is true. When David asked God, he was told an unfailing word. God told David that he and his men will beat the Philistines. God's promises in our life are the same. Why cast doubt because of others non belief. Your facing life's difficulties and you know what God has promised us healing, blessing, and favor. David let his men doubt enough that he had to go back and ask God again. God will give you the same answer as before. But if you let the world cast doubt in you, go back to the One who made the world. The One who will not fail you. Reassure yourself in Him!