Imagine that you hear a sermon. A friend of yours was there as well, and says to you afterwards "he said 'such-and-such' but I have to ask myself 'does it show?' and I have to be honest and answer, to my shame, 'not really.'" How would you respond?
What is the relation between the truths of the Gospel and what we do?
Here is a truth: we are saved by grace. Here is a corresponding action: forgiving one another. Suppose you found yourself not forgiving others. What do you do with that? Do say "woe is me, I'd better try harder"? No, if the truth which forgiveness is supposed to show is God's grace, then if you are not showing it as much as you ought, it is because you do not understand it fully. Thus, if we sin, the solution is to seek the truths which we were supposed to be showing.
Now, where are those truths? Scripture. And how is it that we come to understand them? By God's revelation through his word by the Spirit. That is to say, they are there in Scripture, but we can only understand if God gives the understanding. Indeed, only in knowledge of God is there knowledge of Scripture, since that is what is involved when the Spirit reveals anything to us: The Spirit joining us to God in Christ.
But look at what this means: If we sin because we do not understand, but can only understand if God gives understanding, then we are totally dependent on God for any good we do. We are dependent on him, not only for life (Christ paying the penalty for us), but for living (Christ living the life for us). Thus if we sin, the response should be "God, please, show me what I do not understand for I am helpless to do good apart from you." Now, you may have all the factual understanding, but what we must have if we are to act on it is an experiential understanding. We must get it, or it will remain facts, like the times tables, to be merely spat out in answer to questions. We must understand it into our lives, so that we can live answers to the questions that we are asked in our living, but only God can effect this.