Career Expert Roy Cohen says there are some things your boss never wants to hear, and the worst three things are 'I quit,' 'I'm pregnant,' and 'I'm bored.' Cohen says quitting your job and going to work for a competitor is tough for your boss. If you are a valued employee, then you owe your boss the courtesy of an explanation and a reasonable notification period - two weeks at a minimum. He says your boss will be called on to serve as a reference at some point in the future. He adds that you should always leave on good terms; express gratitude and never complain. Emphasize all that you learned, how difficult this decision was, and that the new opportunity was too important to pass up. Saying you're bored is another tough one for your boss. TheStreet's Rhonda Schaffler has details from New York.