Or perhaps the day after tomorrow...
Another factor of road rage is territory. To many drivers, their cars are their second most valuable possession, so they want to protect it. And if anyone gets in their way of hurting their car, they will react in a violent manner.
Then there is the drivers' ego. Remember everyone on the road is an idiot except for us. Some people associate their driving with their self-esteem, which leads them to think that they can take more risks than others and that they can criticize or harass inferior drivers. Many drivers with big egos believe that nothing bad can happen to them, until something does.
Yet another cause of road rage is selfishness shown by drivers. These drivers just aren't courteous of others and only care about what they're doing and how they're going to get there. Many of these drivers don't obey the rules of the road which can lead to trouble.