Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
The notion of catharsis holds that frustration and anger should not be bottled up or else a person risks allowing those feelings to accrue and eventually explode in some harmful way. Instead, it recommends that frustration and anger should be released through harmless expression, such as by screaming or punching a pillow. However, experimental psychology has shown that such expression can increase rather than decrease harmful behavior. In one experiment, people who engaged in catharsis (by hitting a punching bag) were significantly more likely to aggress toward a peer shortly afterward than were people who did not engage in catharsis.