Take a lesson on properly burning your bridges from Greg Smith, a former executive director at Goldman Sachs. In his resignation letter, Smith calls the environment at the firm "toxic and destructive," notes how he feels the firm has shifted its focus from the client to just making money, and says he knew it was time to leave when he could no longer tell potential employees "what a great place this was to work." A copy of Smith's resignation letter was placed on the Opinion Page of Wednesday's edition of The New York Times. Smith started with the firm 12 years ago as an intern. Before his resignation, Smith was "executive director and head of the firm's United States equity derivatives business in Europe, the Middle East and Africa."