Lloyd-Jones makes a great point in the quote below. The only thing I would add is that many people today think that simple preaching of doctrine will automatically lead to a transformed life. Lloyd-Jones is right when he says we must be taught to think. We need practical guidance to help us apply the wondrous truths of the gospel, or we will remain stunted and immature Christians. Where is the preaching that will help us live as Christians?
Nothing happens automatically in the Christian life. That is a very profound principle, for I believe that most of our troubles arise from the fact that we tend to assume that they do happen automatically. We persist in holding on to a semi-magical notion of regeneration which teaches that, because of what has happened to us, the rest of the story is, quite simply, ‘they all lived happily ever after’. But of course we know that that is not true . . .Obviously the antidote to that is to think, to have an understanding, to reason the thing out thoroughly. The world does not do that. The trouble with the world, ultimately, according to the teaching of the Bible, is that it does not think. If only people thought, most of their problems would be solved . . .The fallacy of the humanist is, of course, that he believes that all you have to do therefore is to tell people to think. But as long as they are sinners they will not think. These elemental forces are so much stronger than the rational forces that ‘man in sin’ is always irrational.
When we become Christians we still need to enforce this self-same principle. Even the Christian does not think automatically; he has to be taught to think—hence these New Testament epistles. Why were they ever written? If a man who becomes a Christian automatically does the right thing, why did the Apostle ever have to write these epistles? Or if you can receive your sanctification as one act, one blessing, why were these epistles ever written? Here they are, full of reason, full of argument, full of demonstrations, full of analogies and comparisons. Why? In order to teach us how to think, in order to teach us how to work these things out, and how to gain understanding.
David Martyn. Lloyd-Jones, Life in the Spirit in Marriage, Home & Work : An Exposition of Ephesians 5:18 to 6:9 (Edinburgh: The Banner of Truth Trust, 1974, c1973), 209.