@Steve McQueen said some very powerful things, and I hope you give him their due.
why would you want to be on bad terms with a woman?
Apart from "a" in that sentence, I agree -- I would put it, "Why would you want to be on bad terms with the woman you obviously had such affection for?"
But being on "good terms" doesn't mean being her lap dog, doesn't mean sitting on your sofa doing the old Mope'n'Hope.
It just means treating her at least as well as you would the United Package Delivery deliverer. "Hey, Charlie, how's it going? Good to see you again."
Even if she doesn't treat you that way. Especially if she doesn't treat you that way.
you asked, "Last resort technique, what to say?" You say nothing. You dont give any ultimatums; dont make any grandious statements that you are through and done.
The good @SMcQ is spot-on. If you "say something," then it's not really a Last Resort Technique. Because if she responds in This Way or That Way to what you say, then maybe (probably) you'll keep hanging on. And then you'll have to have another "last resort."
A Last Resort is just that -- the LAST thing you're going to try. So think about what that means. Your wife told you to let go, to move on. respect her request.
This is all you can do. This is the only true power you have. I did it. And once I did it, and it was obvious to my WAW, suddenly the power completely shifted in my favor. Now in my case events moved somewhat beyond where they theoretically ought to have gone -- but that's another story. The point is, the Best Thing you can do is exactly what she wants you to do. Because then she'll be in that most unenviable of positions for the Walkaway -- getting what she wanted. And not having you to blame.
