We tend to forget, that there is always a choice.
There may be some of you, who think that they had no choice. There was no-one else, the finances did not permit it, etc.. However difficult or improbable it may sound, the fact of the matter is that you have chosen to be the primary caregiver.
You could have left the patient in a hospital, institution, by themselves, with hired help, or even worse case scenario, to deteriorate without adequate care. You have chosen a difficult job, because you cannot tolerate these unwelcome options. Therefore you have not been constrained into this role, but finally, have made the only apparent choice. The only one your heart and conscience allowed you to see.
Reminding yourself that you have chosen this situation, helps increase tolerance and patience, substantially. It also decreases the frustration.