The Christian life is a life of faith. We became Christians by faith in Christ apart from works. And now that we are Christians, we serve God by faith. We walk by faith, not by sight!
An inglorious scene is recorded in Matthew 17:14-21. While the three disciples, Peter, James and John went up on the mountain to see the glorious vision of Jesus coming in His kingdom (Mat. 16:28-17:13), the remaining nine were below failing in their ministry. They were not able to cure a demon possessed boy of epilepsy who was brought to them by his father (Mat. 17:14-21). Though they had been given the power to heal and cast out demons (Mat. 10:1), they failed to exercise faith in God.
If we as Christians, are to be successful in our service to God, we must trust God to use us. He has given us, and will continue to give us all we need to effectively serve and please Him!