Forbidden desire

Christian preachers and moralists condemn lust, but often fail to define it, or define it with precision. To his credit, John Frame offers a definition: 

Lust is specifically the desire to engage in sexual acts that are contrary to God's law  J. Frame, The Doctrine of the Christian Life (P&R 2008), 767.

A friend of mine (Kevin Vasquez) asked me a question about that definition: Are Christians guilty of lust if they have the forbidden desire? What if Christians don't wish to break his commands and yet they have those desires.

That does expose an ambiguity to the definition. It pries apart two aspects of "lust" thus defined. The object of lust is a forbidden desire. Does this mean that by having the desire, you desire to do something forbidden? That's unclear. Does that mean you want to break God's law? It might seem logical to conclude that if you want something contrary to God's law, then indirectly, your desire includes a desire to break God's law in the process. But are these separable?

We might draw a distinction between the desire to have something and the desire to do what's necessary to get it. I might desire the end-result, but I don't wish to do what it takes to get that experience. 

Suppose I'm the son of a military dictator. I'd like to sleep with the girlfriend of my best friend, and there's nothing he could do to stop me, but I refrain out of a sense of honor, or because his friendship means more to me than having a fling with his girlfriend. 

So the agent is conflicted. He has contrary desires. He wants to have it, but he doesn't want to do wrong to have it (even though he could get away with it). Is he still guilty of lust? He exercises moral self-restraint. Doing the right thing overrides wanting the wrong thing. 

I have a forbidden desire, but I have no desire to act on my forbidden desire. Indeed, I have an opposing desire not to act on my forbidden desire. A countervailing desire to resist the forbidden desire. In practice, that neutralizes the forbidden desire. 

On Frame's definition, it's possible that he's still guilty of lust, but is lust still blameworthy in that situation? Does the desire not to act on the desire mitigate or exculpate the desire? 

Alike an unbeliever, a believer is conflicted. So there's a difference. Does the contrary desire not to break God's law morally cancel out the forbidden desire? 

Of course, something that's blameworthy might still be forgivable. On Frame's definition, the desire might still be culpable but forgivable.