Sentence:  Particularly hard 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 <WSD>part</WSD> of himself , he finds distinctly unwelcome . 
Meaning of the word marked with <WSD> tags:  something determined in relation to something that includes it