I never yelled at my players much. That would have been artificial stimulation, which doesn't last very long. I think it's like love and passion. Passion won't last as long as love. When you are dependent on passion, you need more and more of it to make it work. It's the same with yelling.
If a secret history of books could be written, and the author's private thoughts and meanings noted down alongside of his story, how many insipid volumes would become interesting, and dull tales excite the reader!