Here is a line of thought I’ve tried to develop a bit before:
Too often we Christians are heard as saying something along the following lines: “Your life of casual sex (or cohabitation, or homosexuality) surely must be leading you to feel empty, unfulfilled, and jaded. But we have the solution for those unpleasant feelings!” To which the reply is often: “I’m sorry to disappoint, but I don’t feel excessively guilty or ashamed or unfulfilled. On the contrary, my gay partnership has given me more emotional peace than I’ve ever had.”
In other words, we Christians are often found making Stendahl’s mistake: in our rush to defend our understanding of sin and human flourishing, we too easily assume that the same emotions must be the universal human result of certain behavioral choices. When those expected emotions aren’t present—when Paul, for instance, feels no guilt after persecuting the early Christians—we’re suddenly left wondering what went wrong with our doctrine of sin.
I’m not sure I’ve said it here any better than I’ve attempted to say it in the past, but perhaps bringing in the counterpoint between Stendahl and Bonhoeffer will turn out to be illuminating for others, as it was for me.