I fear my H will change but when it is too late or when he settles down with his next family...
We have been through one separation. He had a consciousness of breaking the cycle...we were in counseling, he expressed regret and remorse...there was however a subtle implication that his guilt was pervasive and almost an excuse to give up on really succeeding as a couple. I don't know if that makes sense. I've read it on other threads...some Ss actually saying they themselves had screwed up too much and done irreparable damage etc.
My H has told me that leaving was the most respectful thing he could have done. Whatever. As you said, when one is on a certain track...the justifications are plentiful.
But, I do concede that a) I don't know what he really thinks/feels and b) it is much harder for him to pull this off than it was for his father (whose father had died when he was young)...there will probably be no peace for my H, ever...without some real catharsis. I only hope I and my children can feel whole and peaceful regardless.