Sentence:  Particularly <WSD>hard</WSD> for the therapist to grasp are those instances in which the patient is manifesting an introject traceable to something in the therapist , some aspect of the therapist of which the latter is himself only poorly aware , and the recognition of which , as a part of himself , he finds distinctly unwelcome . 
Meaning of the word marked with <WSD> tags:  not easy; requiring great physical or mental effort to accomplish or comprehend or endure