Being aggressive is one of the key winning factors in sports, but it has nothing to do with yelling, screaming, or cursing. No matter how big pressure you are under, you should keep yourself under reasonable control. Even if you lose your control, then you should apologize sincerely for your behavior. Serena did neither. What a shame. She not only disgraced herself, she also disgraced tennis.
What a disappointing moment in the history of US Open tennis.
Story background: http://www.cbssports.com/tennis/story/12196880