Anger stems from the inability to deal with a situation.
The frustration from not being able to find a solution swells up in order to break through a personal limit and resolve the situation by the most direct way visible - brute force.
This process makes sense on the instinctive level where quick reflexes are needed to survive. In these situations it is better to make a decision immediately (even if it is not a very good one) rather than stall for even a moment.
You take all the incomplete knowledge and strength in your possession and attempt to break through in one burst.
The problem of anger arises when you make an attitude out of this process and try to apply it in social situations. Social situations usually require balance, finesse and resolve, not the brute force anger aims to produce.
With anger you build up all this energy and then you don't know what to do with it. At this point there are two choices: either shut the anger tight within yourself or let it burst out immediately.
If you decide to close away the anger within yourself, it will rot and fester there until it becomes hate (directed at yourself or others).
If you let the anger out, it usually poses a problem for your environment, but there is also a brief moment of relief.
People who develop anger into an attitude basically become anger junkies - chasing that brief moment of relief or satisfaction which requires ever greater amounts of anger to achieve. At this point it is usually easier to follow this path of self-destruction deeper rather than stop and reflect upon what you are doing.
So how to deal with anger?
First of all, if you have become and anger junkie, you have to admit it to yourself.
In specific situations, when the inability to handle it arises, you have to put things into perspective: look at the worst case scenario, accept it, overcome the fears within it, and then the whole negative construct will crumble to ashes.
At that point, you will be able to see at least one solution and act on it with natural grace and elegance rather than anger.