They say that signs of a spouse committing adultery can be pretty clear. They usually express a desire to get away from the home. They usually become completely different people than they were before. And they usually rid themselves of the strongest moral voices in their lives.
I found this last one to be very interesting. I have never really thought about it before, but that makes total sense. If you don't want to feel like scum, you get rid of the voice that would tell you that you are. Notice, it's not that the voice is telling you that, but an adulterer will rid himself of the voices that are most likely to make him feel bad about what he is doing. Once these voices are out of the way, the fantasy world, where evil is committed under the pretense that it is really a kind of good thing, may continue.
This is why so many long term friendships end at the point the individual starts or has committed adultery and wishes to justify himself somehow, that is, if the friend is a strong moral voice. An adulterer will often multiply his non-judgmental "friends" and acquaintances at this point. In fact, that is a common reason that new friends are added during this period, and perhaps, why the adulterer's personality has changed so much (i.e., in order to accommodate the new lifestyle and friendships).
The friends who are left behind ought not feel like they did something wrong. This happens to the Holy Spirit daily. When people sin, they do not wish to hear a convicting voice that tells them they are evil for indulging in that sin. They don't want to hear about the move they are making to dishonor God, destroy those around them, and kill themselves. They want to hear supporting voices. They want to hear understanding voices, who may not think what they are doing is ideal, but still accept their choices as valid. People are justifiers of their own evil, and a strong moral voice throws a wrench into that justifying machine. It challenges the justifications of the fantasy world, where evil is done for good reasons without eternally devastating effects.
In essence, the removal of the strong moral voice in one's life is a sign of God's judgment upon the person. It is to ensure that the choice of the person to engage in evil will end in vindication of God and justice for the victims involved. The mind has been given over, and the end result is a complete execution of who the individual once was as a thinking and moral human being. Only an unreasoning animal, good for nothing but to be trapped and killed, as Peter would say, remains.
It's a terrifying thing to fall into the hands of the living God, and ridding your life of strong moral voices that would call you to account is the sure sign that such a terror is at hand.