I have had moments precisely like you have described. And I did exactly what you did - just decided I wasn't going to let myself fall in that big, black hole of unhappiness. And it works...almost every time.
OK night. My MIL (with whom I get along well) is here tonight - hey, my W is sleeping with someone in her bed - my MIL. W left a book out - pretty careless- entitled "The Good Divorce." That title always makes me laugh in a sad way. I knew she was reading it, but was angry she left it out where S-9 could have seen it. Got that frustration out at the gym. Overall, not something that made me feel good things about W.