Gait training physical therapy can be incredibly frustrating. My father worked with athletes who had to rehabilitate after injuries and invariably he was having to be a counselor as well as a physiotherapist.
At one point he was doing the same thing for his own father after he had a stroke. It was quite heart breaking. Because you expect the muscles to work in the same way, but they don't and having such a basic thing continue to go wrong over and over can just be so difficult to bear.
When it is a stroke victim and they are having to work on other issues as well, it can be quite overwhelming.
But don't give up hope. Eventually you or your loved one will get better.