Failure is impossible, but not because the patient will eventually succeed at whatever task is assigned. Therapists certainly will sometimes choose a task that is too advanced, too far beyond the client's current level of skill. Eventually the trainees learn, from their own direct experience, that sooner or later the therapist will succeed in coming up with the right exercise, and then the client will eventually produce the right articulatory gestures. For people who do not have access to such resources, an alternative plan had to be developed wherein the sessions that the patient can afford are done with a family member of friend or volunteer present, someone who can learn the technique and then continue to work with the patient with occasional guidance from the therapist, long after the money has been used up. Intentional language is generated to accomplish some purpose of the speaker.
Global aphasics have no intentional language.
However, they will never regain any intentional language at all. It may be that someday a mode of therapy that works for them will be developed, but Hildred's definitely does not. I had already read everything there was to read about Hildred's work, and discussed it over and over again with Christine, and it wasn't enough. The sand sloped up from the water, up to a low ridge, then down several feet and then up again, forming a shallow basin behind the front ridge. A storm had come in at high tide and left ponds of stagnant water stranded in the basin, all along the beach.