How do you control anger ?

You just ignore it and you choose to be happy.

When people are rude or I find that they're offensive bla bla bla I get annoyed and angry.
But when I'm calm and happy, it's easy to understand that there may be reasons that cause people to become rude and it doesn't bother me that much. also when I'm busy with other interesting stuff.
Note Keyword : Calm and Happy and Busy with interesting stuff.

I even still get angry at stuff that's happened to me at the past, it was like 3 years ago.
It's crazy how I'm still holding on to that unhappy angry feeling right ?
Here's how it went :
I asked my friend to buy me a CD, I wrote the singer & album name on a piece of paper and gave it to my friend.
So he bought me the CD, but it was a different album, so since the CD shop was near my friend's office, I asked him to exchange it for me.
So he did, and got me another CD, but it was still the wrong one.
(My friend didn't check the CD, he's one of those people who asks for something and pays without checking the thing, but a good friend though ;p)
Anyway, I was so annoyed, so I called the shop and told the guy that it was the wrong CD
so he told me to just bring the CD back and exchange it with another one.
then I asked him, "Do you even have the CD that I wanted?"
then he said "No, but we have other stuff"
Unbelievable, right ??!!! So this guy was just trying to sell any CD to me.
So I asked him to just refund my money and he said "It's only 15$ anyway, what's the big deal?"
at that point I knew that I couldn't talk to him anymore and he's not going to refund my money and whatever I say is not going to make things better so I just hung up.
End of story, but up till now I couldn't let it go.
When I'm reminded of that story, I get angry and annoyed and I just can't understand why someone would behave like that.
So I know I have to let go, forget and forgive and let go.
Letting go is so simple, but I find it so hard to do.
Why ? because I don't want to let go, because if I hold on to that angry feeling, I know that I'm a better person than that CD guy, that I'm the victim, that I'm innocent, I think that's why I hold on to that.

But let see,
I know that when I'm calm and happy and busy with projects/works that I'm excited about, that little annoying story doesn't really bother me.
And I also know that if I get angry, My health is also at risk, I'm ruining my own health, inside and out. So it all depends on myself how to react in similar situations.
People are not going to stop being rude, there always will be annoying people.

So I have a choice, and I want to make that effort.
I will ignore it
I will forgive.
I will forget about it.
I will let go.
I choose to be calm happy.
and on top of that, I'll always get myself involved in an super interesting project so I'm always focused on exciting stuff and no time for other unecessary things.
I want to control myself, I want to be happy no matter what the situation is.

What about you ?