Sentence:  For example , one hebephrenic man used to annoy me , month after month , by saying , whenever I got up to leave and made my fairly steoreotyped comment that I would be seeing him on the following day , or whenever , `` You 're welcome '' , in a notably condescending fashion - as though it were his <WSD>due</WSD> for me to thank him for the privilege of spending the hour with him , and he were thus pointing up my failure to utter a humbly grateful , `` thank you '' to him at the end of each session . 
Meaning of the word marked with <WSD> tags:  that which is deserved or owed