And I said: "So then, I'm hearing you say you were miserable in our M for less than three months and then actively went out looking for another woman. Is that right?"
This cross-examination was not cool, Train.
You know I'm not speaking from personal experience here, but I've worked through a lot of "Given x, how could I ever..." situations just to try to figure out where I would stand on a lot of issues. (I don't like catching myself off guard!)
I think the security and trust will come from addressing the root causes to the demise of your R. If you have openly and honestly and exhaustively gone through the issues you each had, and if you see them regularly being addressed, then you regain that sense that you are caring for each other. And I don't mean that you kinda think the issues are addressed, but you explicitly see that he's not pushing the wrong buttons, and he is pushing the right ones, and that couldn't happen randomly by accident, so he must be consciously making the effort.
And again, it's the root causes that you're watching, not the crap that happened during the A - that's all mindless fluff.
Remember the whole consistent changes over time thing? It doesn't just apply to the LBS getting the WS back; it applies to the WS getting the trust of the LBS back.