Webster defines doubt in this way: "to call into question the truth of; to be uncertain or in doubt about."
We all have doubts. They can be as simple as looking at a cloudless blue sky and not quite believing the weather report that called for showers, or they can be as deep as questioning the very existence of God. Even for the most godly, there will come times when faith is at odds with what we see and feel.
When difficult times overwhelm and prayers seem to go unanswered, the natural reaction is to question the goodness of God. If He is good, and if He cares, where is He and why won't He help me? The truth is, God wants these times to draw us closer to Him - to trust Him to be and do all He has promised. Intellectually we know that is true, but it still isn't easy to have faith when all looks dark and hopeless.
God doesn't ask us to have absolute, unquestioning faith before He will move. He says, only a little will do. God specializes in taking the weak and making them strong - in taking our little and using it to do great things.
Perhaps it looks something like a simple little acorn. They're only about an inch in length and aren't very impressive. It's hard to see what great things they might accomplish. However, given the right conditions ...
they will one day grow to look like these grand oaks, standing over fifty feet tall, with spreading branches that provide shelter and protection. Even when their lives come to an end they will supply warmth and comfort.
Jesus said, "For truly, I say to you, if you have faith like a grain of mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move, and nothing will be impossible for you.” Matthew 17:20
We take our little seed of faith and place it in the hands of a miracle working God, In spite of our feelings or the circumstances surrounding us, the things we cannot understand and know, the many times we've failed or the times God has seemed far from us - He will work in our lives according to His great pleasure and our good.