Think of work like the zoo. If you are at the zoo, and a monkey is jumping up and down and otherwise trying to annoy you, do you get mad? Of course not, the monkey has no power over you no matter how hard it may try. Why is it any different when a person tries to irritate you? It's just a simple matter of not giving someone else power over you. Simply making an active, conscious effort to not take what other people or say seriously is way more effective than getting mad over it and letting your subconscious take over.
Same thing goes for drivers really. What can you do about it? Absolutely nothing, so why let it irritate you? Accept what is as what is and move on.
At games (and this goes when you are on your kids in the car too), just remember your kids are always watching and are always learning from you. Your daughters will grow up and think to be angry is to be masculine, because their dad was angry all the time.. which is not the impression you want to leave, is it?
To be physically strong is a completely different plane from what it is like to be mentally strong. Many people use the gym as an escape and a way of denying the present; having a tough workout is just another way to tire out the brain and escape an unpleasant existence.
Anger, at a basic level, is denial. It is the refusal to accept what is. As soon as you can recognize that, the better off you will be.