The best thing I think I heard when I was heading for/going through a break up was:
"she would be perfect if she was just...........someone else"
The thing is, I have never seen a break up where both partners weren't saying that. It sounds as if you were saying "if only he would just....." and he was saying "If only she would just....."
The best thing I could do was stop trying to be someone I wasn't, and stop trying to make "them" into who I wanted them to be, and blaming her because she wasn't able to be what I wanted.
When I turned it around to be "I am leaving for me" rather then "I am leaving because of you" mental health, peace and tranquility returned a bit faster for me.
"To Thine Own Self Be True" then it follows like night follows day etc etc
Hang in there, it gets better