Brigham Young taught that if one has made temple covenants, and then commits adultery, that the atonement of Christ did not cover that and they must atone themselves through whatever punishments the Lord sees fit to inflict in mortality as well as through the suffering of their own conscience.
Now Brigham Young wasn't one to just make things up. But this is so different than our own notion of how the atonement works that I am trying to figure out how it fits in. For one thing (1) what we get in most Sunday School lessons is that it would be impossible for one to atone oneself for committing any sin, much less for something as serious as adultery, and (2) the atonement definitely covered someone who has made temple covenants and committed adultery.
Now I always find it best to side with the prophets and scriptures and I am not aware of a scripture that directly contradicts Brigham Young's disagreement with us on (2), in fact, we do have scriptures about "impossible to be refreshed...", so I am inclined to simply take Brigham Young's word that we are generally wrong on (2).
So then there is the matter of (1). Elder Packer gave a talk on the atonement in which, at one point, at least suggests that repairing all wrong we have done in some matter actually "atones" for that matter, and that Christ's atonement is for the many times that doing so is impossible. That would certainly include all matters involving chastity. Not that I am trying to pit the two against each other, I think their statements have more in common that they appear to diverge.
Just trying to muse this out. The atonement is the object I have studied more than any other. Not that that means anything, there is much I don't know about it. But running into a clear teaching by a prophet, particularly one who knew as much as Brigham Young did leads me to ponder and consider how his words fit into the whole picture.