I find it really useful to be aware of how I think when I am feeling down. When I do this, I can think of ways to challenge the state next time.

Observations:
* Tendency to focus more on negative things, to the point they "seem more real", just because I am paying so much attention to them I am not thinking of comforting or pleasant things at all.
* This "tunnel vision" leaves no room for natural curiosity. Being curious about our environment allows us to consider new possibilities and learn new things. Life is boring when you feel depressed, and boredom itself feeds back into feeling bad.
* Urges towards physical passivity. The worse I feel, the less I want to do (in fact, the less I want to even MOVE!). Physical inaction breeds a sort of "creeping paralysis" where thought and feeling is completely disconnected from actually DOING anything. Again, the process sustains itself unless it is disrupted.
* The natural tendency to withdraw from socializing when stressed becomes exaggerated. It breeds loneliness, but it doesn't occur to me to get rid of loneliness by overriding the withdrawal urges.
* All these things interact with one another until it becomes one big undifferentiated feeling of "EVERYTHING is wrong, EVERYTHING hurts". "Globalizing" thinking errors take hold, eg. "This whole day sucks, what a waste", because I am not thinking in terms of SPECIFIC things being unpleasant.

Homework time for you and I! (gee what fun lol) ... what methods can we think of to disrupt these processes? It may be hard when we're IN the depressed state, but surely we can program ourselves with simple reminders to disrupt the state next time it goes beyond critical mass? Your best methods may not be the same as mine, which is why I wanted to start a thread for brainstorming.