Depression is a State of Mind
Happiness is a state of mind. It is experienced on the inside. Depression is a state of mind that is opposite to happiness. It is a mental condition characterized by pessimistic thoughts and feelings of helplessness and hopelessness. One cannot be optimistic and depressed at the same time.
At some point (likely early) in life a depressed person comes to believe that his/her happiness depends on situational outcomes and treatment by other people. In other words, the depressed individual believes that happiness, joy, contentment, self-esteem, etc. are conditional. As long as things are the way one desires them to be, there is relative contentment and an absence of depression. However, because this sense of well-being depends on external circumstances, it is sensitive to fluctuations and can change rapidly into a mood of despondency should conditions become more unfavorable.
The depressed person feels unable to control his or her thoughts and feelings because they are incorrectly assumed to be governed by outside forces. If those influences are positive, thoughts and feelings are positive; if negative, then the opposite. This is why depression is described by some as mental state of helplessness and hopelessness. When one steadfastly believes that his/her frame of mind depends on outside circumstances and actions of other people, it is inevitable that he or she will eventually become depressed and feel powerless to do anything about it.
It is not possible to control everything or everyone. Failure and rejection occur in spite of one's best efforts. Not everyone attains their cherished goals. Losses and tragedies occur willy-nilly. It is a fact of life. Some people seem to be mostly unaffected by the ups and downs of living and recover quickly from setbacks. However, the depressed person is not one of them. Because of high level of sensitivity to adversity, he/she is profoundly affected and may not be able to overcome major disappointments. Then depression will likely only get worse over time, as depression reinforces depression.
What, then, is the answer to the problem of depression? There are really two fundamental solutions.
The first is a change in life's circumstances so that one's expectations for happiness are finally met. The difficulty here is that the more depressed a person becomes the less likely is that to happen, for depression becomes a self-fulfilling prophecy. The more depressed a person is the less hopeful he/she is about any kind of positive change in life’s circumstances. And so instead of things getting better they only worsen, because there is insufficient optimism and thus motivation to do something about one's dismal situation.
The second solution is a drastic change in one's belief system. As long as one is convinced that attitudes and mood are controlled by others and external events, this is not possible. In such a case, thoughts and feelings are held captive by influences on the outside. However, as soon as one understands that he/she can control his/her own thought processes (and thus feelings), the door to change begins to open. Then, a depressed person starts to become more hopeful about change. He/she realizes that there is something that can in fact be done, because it doesn't depend entirely on other people and circumstances. And the more hopeful (optimistic) a person becomes, the less depressed he/she is.
Depression is at its worst when someone firmly believes that happiness is dependent on things outside of self and at the same time feels powerless to alter his/her unhappy situation.
Being able to shift the locus of control over thoughts and feelings from the outside to the inside of self is what makes possible a beginning recovery from depression.