I personally don't think "Act as if they are never going to return" and Standing go together. One presumes they are not coming back, the other is waiting in hope that they do!
It becomes a matter of you don't need them in your life anymore, but are willing to consider an R if they've done the work on their end.
This is how I thought about that "mantra" Braveheart. My h claimed he could feel me moving away from him. Like you, I had honestly stopped looking. I just wanted to be free from this excruciating pain and "letting go" was the only way I could find to do that. My h came screaming back as soon as he felt the shift. I was surprised, because I was not trying to "trick" him back.
Now, the business about them returning. Oh goodness. I don't think I have seen one single MLCer return COMPLETELY cooked. My friends h returned more finished then my h, but still, HE ALSO WANTED TO SWEEP it all aside. Both of us, had to stand very firm on that, "boundary"! There would be no sweeping this to one side. We would work through all of this, or at least as much as we were aware of, or we would not stay with them.
The beauty of having sorted yourself out, you are honestly capable of LEAVING them. You can live without them, as you have done so already. The truth is, they are the ones who have the most to lose. As most of them have not done the work they needed to do, so they need us, as ROLE MODELS.
As osb has experienced, with TIME they do begin to MIRROR us. WE don't need to be nasty and anger definitely doesn't help, although many of us discovered that "anger" at that time. I really wish I had had it out of my system before he returned, but sadly, I didn't. So we had to WEATHER that, along with him not being fully "cooked"!
Reconciliation is not easy, but if you are both willing to take the chance and do the work, you will be amazed at what can come out of it. Mostly, you have to be true to yourself and you have to be totally willing to "walk away" if it isn't what you both want.
Hugs Stayed