Other thinking.
If there is one lesson I have learned as a result of my divorce it is that once I can move away from other-thinking the closer I am to healing. Other thinking. It can be insidious. At first you are thinking of your other, soon to be ex, when you are in the turmoil that leads to separation. Many of your sentences begin with " If only he would ..." 'Why can't she be more like", "I can't believe he did that!"
Just after separation you may cut him out of your hair, lose a few pounds, update your wardrobe so when he sees the new you he notices, you hope, the changes about you. Maybe he'll find you attractive again. Maybe he'll regret leaving you. Sure signs that you are still entangled in him. Sure signs that you still care what he thinks of you. But in terms of other thinking this is relatively benign. While not completely healthy it at least is not hurting anyone. Eventually, you are given glimpses of why the marriage did not work out. Then you can realize that all this self care is not for his/ her sake but yours. And heck, you got a new hair cut and you look great!
The more destructive other thinking is the kind that keeps you up at night. This is the sort that has you thinking about division of assets, sleuthing the truth as to why he left, hyper-vigilance over every contact with the kids. It is the kind of thinking that you dull with wine. You have long one-sided tear stain conversations with friends. You obsess over details of fights you had years ago. It is the kind of thinking that is an expression of the incredible stress that divorce can wreak on your soul.
It is the kind of thinking we all go through. I am sure that my ex went through the same thing. Only after it is all said and done and the papers are signed can you really move beyond other thinking. For your own happiness you should move beyond this kind of thinking. Who cares if your ex has a new boy/girlfriend? That person will have to deal with his dirty underwear on the floor. So your ex has a shiny new car , a boat and you have a 20 year old car, you need to find your own happiness and not dwell on his stuff. What matters most at this point is whether the other parent is fulfilling his obligations to your children.
Because if there are kids you have to move beyond it. I don't mean to state this as though I have all the authority of a self-help book. I say this because my parents were divorced when I was 4 years old. This is the recurring memory from my childhood: my mother with a can of coke on the kitchen table, a cigarette in her hand burning down to a long stick of ash as she is ranting to someone on the phone about my absent father. Throughout my adulthood I have had conversations with her that revert back to my father decades after he left. For her it is not the past retold, the pain and hurt are still very present. All this energy, anger, and bitterness expressed towards someone who has not been part of her life since the 1970's. Sad. I can only imagine how much happier she could have been; and as a result my childhood, if she had been able to move beyond her grief.
When I think about what I want my son to remember about his childhood it is not a constant stream of arguments between his parents. It is not a mother blinded by anger and pain at his dad so much that she denies her own happiness. There may be lots of changes and sacrifices that I have had to make as a result of my divorce and single parenthood; but my chance to be content in my own skin is a sacrifice I am not willing to make. It serves no purpose. There will always be collateral damage employing this strategy; and he is four feet tall, has curly hair and glasses. So with time and distance and forgiveness and honesty with myself I try really hard to put the other-thinking where it belongs, in the past with my marriage.