From Psychology Today

Anger, pain and depression are three negative experiences so closely bound together it can sometimes be hard to know where one ends and the other begins. Pain is a complex phenomenon that has emotional and physical components. The emotions play a huge role in the experience of pain, and pain is intimately associated with depression. It's long been known that the psychic pain of depression feeds anger. But just as often, anger fuels depression.

A powerful emotion physiologically and emotionally, anger often feels good—but only for the moment. It can be a motivating force that moves you to action. But there are good actions and bad ones; it's vital to distinguish between the two.

Many people confuse anger and hostility. Anger is a response to a situation that presents some threat. Hostility is a more enduring characteristic, a predisposition, a personality trait reflecting a readiness to express anger.

Anger is usually anything but subtle. It has potent physiological effects. You feel it in your chest. You feel it in your head. You feel it coursing through your body.

Nevertheless, anger can be insidious. Anger confers an immediate sense of purpose; it's a shortcut to motivation. And if there's something depressed people need, it's motivation. But anger creates a cycle of rage and defeatism.

When you feel anger, it provides the impulse to pass the pain along to others. The boss chews you out, you then snap at everyone in your path. Anger, however, can eventually lead you into self-pity, because you can't slough off the self-hurt.

Anger is classically a way of passing psychic pain on to others. The two-step: You feel hurt, "poor me," "I hate you." It's a way of making others pay for your emotional deficits. It is wise to change that tendency. Whether or not anger fuels depression, it isn't good for the enjoyment of life.

Here are ways to keep anger from feeding your depression.

• First, of course, is to identify anger and to acknowledge it. Anger is one of those emotions whose expression is sometimes subject to taboos so that people can grow up unable to recognize it; they feel its physical discomfort but can't label it.
• Build a lexicon for your internal states. If you have a word for your emotional state, then you can begin to deal with it. Feelings are fluid; you need to stop and capture them in a word, or else you lose them and don't know you have them. A label improves your ability to understand your feelings.
• View your anger as a signal. It is not something to be escaped. It is not something to be suppressed. It is something to be accepted as a sign that some deeper threat has occurred that needs your attention.
• Make yourself aware of the purpose your anger serves. Be sure to distinguish purpose from passion. Things that have a positive purpose seek betterment, growth, love, enhancement, fulfillment. Things that have a negative purpose are motivated by a sense of deficiency. Your boss yells at you, you feel diminished; the anger you express at others is driven by the blow you've just received. Are you enraged about an inequity or unfairness?

  In order to identify your motivation, you need to look within. It's a matter of becoming psychological-minded and engaging in introspection. Tune into the inner dialogue that you customarily have with yourself.

• If your anger is deficiency-motivated, driven by a wish to rectify a wrong you believe done to you, work on acceptance. Give up your obsession about the wrong. See that the opposite of anger is not passivity but more functional assertiveness.
• Uproot mistaken beliefs that underlie your response. Very often anger is the result of beliefs that lead you to place unreasonable demands on circumstances, such as, that life must be fair. Unfairness exists. The belief that you are entitled to fairness results from the mistaken idea that you are special. If you feel that you are special, you will certainly find lots to be angry about, because the universe is indifferent to us.

  Insisting that life must be fair is not only irrational, it will cause you to collect injustices done to your noble self. Even if you are experiencing nothing more than your fair share of unfairness, such a belief can still fuel rage and lead to depression.

  Those who hold the deep belief that life should always be fair cannot abide when it is unfair. That leads directly to rage that is totally inert, because they believe there is nothing that they can do about the unfairness. They feel helpless and hopeless—in other words, depressed. Self-pity is another description of the same phenomenon.

• Notice your own complaining. Listen for both overt and covert complaining. Overt complaining hassles others. It's really a manipulative strategy. Know when it's becoming a downer and a barrier to a strategy of effectiveness—like complaining about a fly in your soup. Covert complaining hassles you; it drags you down into passivity and inertia. Once you notice it, determine to give it up.
• Once you can accept that life sometimes is unfair, then you can pursue positive purpose. You can work constructively against injustices you find, transforming your anger into passion. Or you can pursue fulfillment in spite of the unfairness that exists.