Know Anger, Know Fear. No Fear, No Anger.
This is one of those things. If you do know it already (like Jon Katz), I don't need to tell you, and if you don't know it already, it's not going to make any sense to you and you're going to fight it. So here goes:
Our anger is almost always based on our fear.
"Hey, waitaminute!" you say. "When that guy cut me off in traffic this morning, he made me angry, but I wasn't afraid of him."
The fear that leads to anger doesn't have to be fear of the person you're angry at. When you got angry at the guy who cut you off in traffic, it was because you (a) felt a loss of control - which triggered deep-seated fears that you would suffer hurt and loss when you couldn't control things - or (b) perceived a loss of dignity - which triggered deep-seated fears that by "taking away" your dignity someone could take away your self.
Imagine, if you can, that you've let go of all attachments. You don't have to be first in line. It doesn't matter when you get to your destination, or whether you get there at all. You don't care what other people think of you, or if they think of you at all. You don't care about stuff. You're not afraid of dying. Whatever happens is okay with you. You fear nothing. What makes you angry? Nothing.
Here's more of a Buddhist perspective on anger.