I certainly have had my fury of racquet throwing, especially at a younger age. As one might expect, I think that mental management of anger comes with experience, age and a *****-load of patience. Another factor, I have found, to affect anger is that of the pressure of the game. Is it a match that has a lot on the line, in terms of ranked playing? For a lot of guys, this pressure is really heavy. For other guys, even though it might not be a tourney, just having your pride being questioned because your opponent, who for no rational reason happens to be winning even though you are ten times better all around than him/her, even though you beat him/her 99 times out of 100, this attack on your pride, often self-inflicted, is enough to make you crack and break down.
Just try to maintain focus and review your game plan. If your game plan isn't working, then revise it a little. The point is, get your mind off of your rage and concentrate on your gameplan, this will almost always get your head back to where it needs to be, and off of the poor racquet that takes an endless beating. It's healthy to let off steam, but don't give your opponent a reason to exploit your anger, this will only empower him/her more. I like the Sharapova approach to regrouping in times of mental strain, that is , just turn your back to your opponent for a few seconds in between serves just to regroup and to wipe your mind from the previous point and remember the bigger game plan you set out for yourself.