There are two things which I am confident I can do very well: one is an introduction to a literary work, stating what it is to contain, and how it should be executed in the most perfect manner; the other is a conclusion, shewing from various causes why the execution has not been equal to what the author promised to himself and to the public.

-Johnson, Samuel known as Dr Johnson
  Quoted in  James Boswell The Life of Samuel Johnson (1791), vol.1.