"In a more recent experiment by Bushman (2002), participants were induced into feeling anger, and were split into one of three groups: one group allowed participants to vent their anger by punching a punching bag as many times as they liked while thinking about the person who had angered them; another group was allowed to punch the punching bag, but instead participants were told to think about doing so for the purposes of becoming fit; and the third group was a control group in which participants were not allowed to punch the punching bag. Following this, measurements of participants' anger and aggression levels were conducted.
The results showed that participants who took their anger out on the punching bag while thinking about the person who angered them, were the most aggressive and angry. Venting their anger did not lead to a positive mood. People who punched the punching bag to distract themselves, for the purposes of being fit, were less angry than the venting group, but were not less aggressive. It seems that even if a person is thinking about something else, just the aggressive physical act of punching something leads the person to be more aggressive as a result. The most promising results could be seen in the participants who did nothing at all, rather than venting. This group demonstrated the lowest aggression and anger levels of all three groups.
It seems that if you ever become really angry, the worst possible thing you could do would be to vent your anger. As Bushman (2002) says, this would be similar to "using gasoline to put out a fire." Venting your anger will only lead you to become more angry and more aggressive. Instead, the best possible advice would probably be to just continue with your life as normal; maybe engage in a favourite hobby or talk with friends, and take your mind off the anger. Do not follow what the movies tell you to do, and vent. It will only make you worse off."
(Quoted from;
http://afmag.net/venting-your-anger-dont-you-are-only-making-it-worse.html , though reading the actual research findings may be good too.)