Yes, don’t be afraid of a breakdown, but think.... What do you really think if you no longer have your ML girl in the picture? Do you need her around so you can move on to her? Is it just new and exciting versus the now mundane? Do you pick arguments to validate your marriage is broken? You should be happier being out of a broken marriage without the third party. Two individual issues, and seeing it’s not primary school solve them one after the other.