This is a subject perhaps best addressed without too many sweeping generalities or absolutes. But to generalize my own ignorance for a minute, a phenomenon I see played out on ATOT all to frequently, I'm going to make the ridiculously uninformed guess that the final word on the nature and source of depression is not clinically established or scientifically consensulaized. We see two camps developing, those see a malaise based on chemical imbalance best dispensed with via pills, and those who see a psychological condition with treatable via techniques, exestencial, or metaphysical. I tried to suggest a possible blending and overlap, the suicide portion of which needs careful attention, drugs if necessary, to combat regardless of origin. There can be, I think, no doubt that chemistry has a role to play in depression and somebody already made clear the absurdly obvious preference for pill over bullet. That there seems to be a genetic component just adds weight to the fire, although the parent component of depression is, I think powerful not only from a genetic point of view, but nurture wise, as in child rearing techniques run in families and therefore so should outcome.
Anyway, among those who see or focus on the psychological component of depression the question becomes is it good or bad. Clearly it's obvious that it's bad if it ruins your life or leads to self destruction and good if it leads to character building, the capacity to empathize etc. Suffering deepens the soul. Trust me.

No pain, no gain, How high you go depends on how low ya been and so on.
But the fact that depression may have a chemical signature does not mean that it has a parallel attitudinal component. My personal opinion is that we live in a depressed society because we live in an unreal world. We watch actors on TV instead of being actors ourselves. But mostly we live in a judgmental, competitive, me first society that cuts your throat first and asks questions later. We live in a society that is anti life, anti person. We have artificial standards of excellence that do not correspond to the range of human types. We are required to conform to a life in a straight jacket. The most insane can do it, the least insane can't fit in. The odd, the freaked, the depressed are just a bit more sane, a bit less able to play dead than the fully adjusted. That doesn't make them better. It is often the fully adjusted, the successful, the socially strong who, out of their strength and self confidence have the courage to not just question, but to revolutionize.
What you see common in this thread is the notion of the tie between lack of self confidence, self respect, and self esteem as diagnostic of a depressed state. Clearly this would imply an obvious source and direction out and or up from depression. Why do people feel bad about themselves? Really why? Can you give one good reason why anybody should not like themselves. Not liking yourself is just not intellectually supportable. There is no reason for it. It isn't the intellect that condemns us it's our emotions. The reason you cannot find the reason you don't like yourself is because it is buried in the unconscious. The reason that novon's suggestion that you set small goals and achieve them both works and doesn't work is that any achievement contradicts the negative feeling, takes you into the land of the achievers, the successful, the ones with the strength to take revolutionary steps like loving yourself, but the reason it doesn't work is because the cause remains out of consciousness and perniciously invisible. It keeps rearing it's ugly but invisible head. Another success, another temporary victory. But enough victories can put you over a threshold into a better place.
What are the potentials of therapy or religious faith. With the latter, with faith that God loves you, with a deep belief that you are loved by God there can come a similar transcending of negative feelings. I may be worthless tome but God loves me and He is bigger and better than me. Take his word for it if you can. Alternately you can dive down into depression, you can let it take over and posses you in therapy. You can go into the feelings of worthlessness and track them down. This is difficult. We evade it with all our might. We see a psychiatrist to become better at being ill, not to face ourselves. But in those rare places, I no longer know of any, where people struggle to go into their feelings, there are explosions of traumatic reliving of events unimaginable that occurred to us a children. It is possible to trace back, to feel how bad we feel so deeply as to completely relive the original event as if it were now, and secondarily, and later see that everything we were made to think about ourselves is a total lie. In this case the belief that we are worthless can be broken totally and permanently because we KNOW exactly why we felt bad and have left it behind.
Depression is an echo of our psychic death, the faint suppressed rumblings of discontent that we were psychically murdered as children, made to feel bad, compared to little Johnny next door, shown we didn't measure up. We are in a bind. To go up we have to go down. We are under a capsized boat. For those of you who are depressed and struggle so desperately to be free, all I can say is that there are those who have traveled to the core of their being and found there only love.
We are chimpanzees. The wild ones have a ball or a banana.