If you have serious road rage, go for serious help. Take a defensive driving course, or ask your local police station what they recommend regarding rehabilitation.
The enemy here is yourself, even if the person ahead of you is driving badly. This is because you are in control of your emotions, not them.
My first recommendation is to reduce the chances of becoming upset by other drivers’ choices, and this is easily accomplished by leaving more space between the cars. As a bonus, you’ll be a safer driver, have more time to react to situations, etc.
My second recommendation is to become aware of your thoughts and emotions, almost put them in a box and observe them as if you were another person. When someone does something that makes you angry, observe your anger instead of acting on it, understand why this anger exists, and think of ways you could have avoided the anger. Understanding is the first step towards eliminating, after all.
My third recommendation is to calm down and keep your cool. Do whatever soothes you, whether it’s music, a conversation, whatever. I find sympathizing also works to cool me down, my mind can invent a situation that results in the way this person drives, this keeps my brain occupied and I don’t feel the need to express myself outwards.