Reposting one of my answers:
There is a reason why people do the things they do, and the reasons are not always good ones. We may interact with a hundred drivers in a few minutes. Statistically, one of those drivers will be the worst in a hundred. One will be schizophrenic; 4 will be bipolar (3 severely); 4 will be sociopaths; 4 will have clinical rage disorder. 1 or 2 will have clinical Borderline Personality Disorder. 7 of them will be convicted felons, 7 will be alcoholics. A variable number will be under the influence of alcohol, cocaine, meth, and all sorts of other drugs. Some will have just lost a loved one, more will have recently been dumped by a lover. 2 will be in their first year of driving; 2 will not be able to continue driving next year. 20 beat their wives, husbands, boy friends, girl friends. 20 will have been beaten. These are the drivers around us.
Our only defense is to keep cool, think like a professional, and deal with the weird things on the road around us. Driving is never personal but it is perfectly willing to turn our lives into tragedies if we let emotions in while driving. Impatience will sure make it a lot worse. We need to be aware that we are juggling chain saws every moment we are in traffic, that we control our vehicle and lots of unfit drivers are controlling vehicles near us. That's just the way it is and we can't change it.