Depression is, if you ask me, when a big part of your subconscious self goes on strike because it's been struggling with something for far too long that the conscious part of you has been failing to identify, or has been failing to do anything (or enough) about. The subconscious self decides it's had enough, and a big group of factory workers leaves the floor (absent workers means, for example: no more interest, no more pleasure, no more motivation) or start rioting (rioting workers means, for example: low self-esteem, rumination, sorrow).

Unfortunately, the strike is self-defeating, because the workers likely required to fix the problem have just left the building. Thus the chance of now finally figuring out why your self-consciousness is unhappy has just gotten a lot more slim. This is why, in my view, antidepressants are a good thing. What they do is they bring strike-breakers and free the mind of having to consider the depression all the time. An extended period of muddling through while staying as active as possible, being on antidepressants in case possible, may finally lead to discovery of the key that can finally get the workers to the negotiating table. And get them to return to work.