My ex did something very similar; at the time he dropped the news, we were five weeks out from a family vacation to Europe. He hadn't filed when he told me, but his mind was made up, counseling wasn't an option, and he moved out within a week. Not a month before I'd told a friend that things were going better between us that they had in years; I knew he'd been stressed in the previous weeks, but he blamed it on work and trying to get ready for the trip. 'Blindsided' fits the bill.

I spent hours in counseling trying to make sense of his behavior, but the closest my therapist came to an explanation was that he pretended as long as he could and he just couldn't take it anymore. He told me that first night that he was "bored with suburban life and wanted some adventure", and even a year out I don't think it was anything more than him not wanting to be tied down to family responsibilities anymore. I don't think him leaving was ever about me as much as he just decided he couldn't do this routine another day.

So, where do you go from here? I endeavored to always take the high road: I gave him documents before he had to ask, I made sure I was upfront and transparent about all the financial stuff, I made sure to never give him reason to suspect I was doing anything sneaky.

We managed to come up with our own settlement terms, and just used our lawyers to type things up and review. As eager as he was to get out, he didn't actually get around to filing for a few months, so things had a chance to settle before we dove into things. I used those two months to do all the research I could as far as getting finances in order, meeting with my lawyer and a financial planner, figuring out what I was going to do in the big picture.

I'm not sure what you mean by "game plan". Part of my being upfront was having worked with a financial planner to set up a support amount that would be just enough to keep me from living off of savings while I head back to school. The reports she was able to generate were invaluable in showing that I wasn't being greedy and that he'd still be more than well-off with that obligation. There was one part of the big picture 'game plan' that I kept to myself, though; no sense tipping your entire hand ;)

Other than that, the only thing that I think saved my sanity was completely pulling back from him emotionally. I realized early on that he was no longer someone I could/should rely on for support, so my communication with him was business only. I figured he was no longer entitled to know anything about me and stopped sharing any personal information.

It's going to be a roller coaster, no doubt about that, but you are going to come out stronger on the other side. With 18 months of time and distance, I can honestly say I'm happier being on my own.