Natural versus Spirit

On page 104 of Gospel Worship it says, "If men act by natural parts, those will not carry them through difficulties and discouragements. But if you act by the Spirit of God, though you meet with such difficulties and discouragements, you will be carried through them all." How much greater are difficulties when, though we are doing the right thing, we do it by our natural parts, and not by the Spirit? I wonder how often I pray for God to help me through something, but I'm praying not truly believing, just praying because I know that's what I need to do?