"Surely what a man does when he is taken off his guard is the best evidence for what sort of a man he is? Surely what pops out before the man has time to put on a disguise is the truth? If there are rats in a cellar you are most likely to see them if you go in very suddenly. But the suddenness does not create the rats: it only prevents them from hiding. In the same way the suddenness of the provocation does not make me an ill-tempered man; it only shows me what an ill-tempered man I am. The rats are always there in the cellar, but if you go in shouting and noisily they will have taken cover before you switch on the light." C. S. Lewis -- Mere Christianity
Understanding this would greatly reduce many of the violent responses we find in society today. A driver who cuts you off did not create your 'anger rat', it only exposed it. That fight you had with a loved one was not caused by their words or deeds, that only turned the light on the rat that was already there.
Those people I know who rarely if ever get angry are usually those who have achieved that most excellent state of being - a rat free cellar. They no longer have the 'disposition to do evil' that they once did. It's not about controlling your anger, it's about no longer even having it.