Your W is at a tenuous point in life. Women especially are susceptible to the "Decade Life Analysis Phenomenon" (I just made that up.)
I knew girls that flipped out over turning 20! 30, 40, and 50 do not get any easier. I know my wife turning 50 was a big part of our problem last year. So she is 40 now, she probably feels like life is passing her by, she has lost herself, and turning 40 has made her take stock of what she wants in the future.
/not interested in hijacking another thread, so putting this here
At the end of the day, I could never truly discern what W’s reasons are for doing this (shouldn’t mind-read, and I know there are things I have contributed to lead us here), but I do wonder if this was / is a contributing factor—W turned 30 back in May.
