We think having faith means being convinced God exists in the same way we are convinced a chair exists. People who cannot be completely convinced of God's existence think faith is impossible for them. Not so. People who doubt can have great faith because faith is something you do, not something you think. In fact, the greater your doubt the more heroic your faith.
God, I don't have great faith, but I can be faithful. My belief in you may be seasonal, but my faithfulness will not. I will follow in the way of Christ. I will act as though my life and the lives of others matter. I will love. I have no greater gift to offer than my life. Take it.