Muddle, I am convinced that each of us, or at least those of us that really try (and that's just about all of us here) know where our line is. It's different for all of us but suffice it to say it's probably MUCH different than your average Joe for whom the line is cheating. For us, we accepted that and made every effort to move past it, into that nether-land of examining the relationship behind the veil of infidelity. This is a TERRIBLY difficult thing to do and many of us pay a steep price for our self-examination, in addition to the already unbearable toll taken by our WAS's and their affairs.
We decide, through our reading of DR/DB, other relationship books and the support of the great people here, to stick things out, learn about ourselves and in the process, try to save our marriage.
After choosing to do all that, it's natural to keep riding the wave of emotions until the very last minute. It's natural to keep paddling back out into the set of waves for the chance to catch that perfect wave that will lead to the promise of a renewed relationship with the one we love but at a certain point, the waves die and we're left floating on a stick of foam, wood and glass, surrounded by miles of ocean and sharks circling below our dangling feet.
It becomes pretty clear at that point that the day's session is over and it's time to call it a day. Does that mean we won't go back out again? Nope, but it does mean we're not stupid enough to just sit in still water expecting a perfect wave to emerge on the horizon.
You KNOW when you've had enough. You know when it's time to paddle back in and dry off for awhile.
You KNOW you've given it your all but no amount of wishing, technique or experience is going to manufacture the wave to surf on and in our sitches, the R is the wave and our spouses are mother nature, lending the right conditions that allow us to display our skills.
You are a much different man than when you started all this and the fact is that she hasn't either see that, or stopped to care. She is on her path and until she decides to change that, you probably won't move forward very much.
You KNOW when you've had enough and the fact that you have the understanding of yourself AND this kind of sitch to know it doesn't mean the end is testament to your growth.
This is just another stop on the road. Do what you have to do here and make sure you take care of you. Don't allow yourself to be part of a sitch that you don't want to be. Set your boundaries and establish your own way of living, with or without her approval.
I think you will do find Muddle. I have always had faith in you. I just think it's time you showed her you have faith in yourself by just living up to your standards, not down to hers.