You don't have to go to the extreme to give examples, as Cyrena says, because they are not bound to be real. Although I have read about it here, fortunately it hasn't happened to me.
I do believe though that because we are all civilized humans, brought up with the right values and traditions, we should know what they are. We don't even have to talk about it, rehash it all the time. I find all that sitting down and discussing things pointless.
And I do have a boundary, in a way. It will be what I call my own point of no return. And when that is reached, I will just end it all. Sorry, no warnings, butI think my H knows what those are.
Here's the lesson I learned about how civilized human beings brought up with good values react to their desire to do someting instrinsically wrong, like an A, or maybe some other thing like trying out drugs (both real life and condensed from reading stuff here and elsewhere)
1. They at first fight it 2. They can't fight it so they start fantisizing about it, and start justifying why it is OK, alhtough inside them they are not fully convinced. 3. They do it anyway, just a little, maybe hoping they can get away with it, and nobody will be hurt. 4. They get caught, and this is when they start believing the rationalizations and justifications they made. 5. Pride comes in, and they defend their actions. At this point, they don't care who gets hurt. They don't see others getting hurt. When others try to make them see what they did wrong, they fight back and rebel. Sometimes, they caught in this stage and never leave it. 6. They realize that they hurt others, but still prideful, they carry on. They may stop doing what they did but they are still justifying that it was not wrong. Guilt mixed with pride. 7. Acceptance of what they did wrong. Making amends and repartions. Might be too late, especially if they had cut ties.
My point here: if you have a wayward spouse or child, there are certain points that nothing you could say or do, not even boundaries, can stop them.
You have to rely on the fact that before that happened, they already know what's right and wrong.
Me:49 H:45 D:12 M:14 T:18 Bomb: 6/26/10 EA: 9/3/10, fizzled out slowly, now ??? 11/5/11 Retrouvaille Finally piecing.... Its peaceful at last, but we got a looong way to go