I've commented about this before. I had an ex who I was with for three years. After we moved in together, he stopped trying. When I would be an emotion that was anything other than chipper, he'd basically ignore me. I tried communicating this to him, and even scheduled a couple's therapy appointment. He refused to go, saying that he couldn't because of work and that one session was enough. The therapist was clear he'd work with us on our hours, especially since he had many clients who were also in my ex's line of work.

I left. I gave him so many chances, he didn't want to improve, he'd maybe try for a day or two and fall into old patterns. Some people do not want to or do not have the capacity to change.