Doubt. We all have it. Faith or no faith. Even Mary had her doubts.
Did you notice Mary's first reaction after the angel Gabriel's greeting? She was afraid, even after the angel greeted her with praises. She was already filled with uncertainty. Gabriel then tells her she will conceive and give birth to Jesus, the Son of God. What is her response...how? "How will this be?" Her first reaction to the news that she will be the mother of the Messiah isn't excitement. She questions God.
Doubt could be our evidence of growth. The stronger we become in faith, the more questions we have. The more we dig, the more we wonder, the more we learn, the more we seek. God didn't choose Mary because her faith was weak. We can't find the answers to our questions if the questions are never asked. Maybe our greatest gifts can be on the other side of our doubt. Mary's was.
If we had proof right away what would we even need faith for? However paradoxical the two may seem, faith may not grow without a little doubt to begin with.
My lingering doubt is not of God's ability. Will I understand His answer?
If we seek to only have faith when all our doubts are answered, what will get us through our troubles in the first place?