understand that shadow aspect of yourself. You get upset in the car, as do many of us, because you desire not to be hurt, you desire others not to be hurt, you desire to get to your destination in a timely and safe way. This is self preservation, not just of your physical self, but when extended to others, of your moral self. You get angry first in relation to your body being put in danger, then you realize this and dissaprove of your own anger, thus you rationalize your anger as concern for the wellbeing of all those on the road up to and including yourself and maintain your moral stance of compassion for and respect for all life.
Drive safely because it is what must be done, accept that many others on the road will act selfishly and adjust accordingly be avoiding them. This is balance.