Preface http://books.google.com/books?id=aniaAAAAIAAJ&q=%22No+man+who+is+occupied+in+doing+a+very+difficult+thing+and+doing+it+very+well+ever+loses+his+self-respect%22&pg=PR22#v=onepage
1910s, The Doctor's Dilemma (1911)
Variant: No man who is occupied in doing a very difficult thing, and doing it very well, ever loses his self-respect.
