Here's an example of what can happen when you completely misjudge your case, your audience, yourself... Follow this link to the 7th Circuit oral argument page for the case of U.S. v. Johnson. Then follow the hyperlink "Oral Argument" to the audio file to see just how bad things can get.
After counsel's attempt at oral argument, the case went on to be decided; the full opinion appears at 123 Fed.Appx. 240, 2005 WL 589976 (2005).