Anger is the gatekeeper of our emotions. If it is used powerfully, it will provide us to interact with the world fully aware of when our emotional gates should remain, open and when to keep them closed.
Imagine the gatekeeper for a moment. She knows that her job is to protect. She also knows that if she is over protective those inside the gate will die from starvation or suffer from a lack of exposure to the outside world.
In the same way, anger protects our most vulnerable emotions. When we feel emotions like fear, disappointment, pain, grief, loss, rejection, humiliation, jealousy, being taken advantage of etc. anger forms a protective layer to keep others form further exploiting us. This is a wonderful tool in our emotional arsenal. Sadly just like the over zealous gatekeeper who keeps the gate close-anger can be destructive by fostering isolation from ourselves and others.
When our anger is appropriately, others will know through good communication that we have been negatively affected by their actions and in turn we can take steps to meet our own needs to ease our pain, disappointment, embarrassment etc. without becoming uselessly angry.
The Anger or the Emotional gatekeeper, which protects our other emotions however we need to also remember that there, is a slight balance between protections and suffocation.