Another day gone by and still retaining the mindset! Again, I still don't feel well, no, I still don't feel good-- but each time I find the same ruminative thoughts starting to creep in (a fantasy about telling her what a selfish and sadistic person she has been, and having her actually feel awful about it) I can block them by remembering that I was stupid to have married her instead of just being her "boyfriend" all these years. The destruction of our marriage is her fault, but this consequence ultimately isn't something she did to me. I brought it on myself.
I suspect this thought is working, at least for now, because it seems to give me at least some of the power and agency that I forfeited to her. I haven't been cheated out of the past ten years of my life by her. No. Rather, ten years ago, I made a mistake. Now I've paid for it. I can't now do anything at all with W-- I'm powerless. But for myself, I can do my best not to make the same mistake again. I have the power to do something.
I'm not going to fool myself into thinking that this is a magic mindset that will solve all my emotional problems. But it may continue to serve as an effective management tool.