I think this is the hardest part of having clinical depression. At least for me if I miss the early signs and get too far down the slope there will be things that I know for a fact will help but can’t make myself do, because I am too depressed to do anything.
The pattern becomes a self-reinforcing cycle, the more depressed you get, the less motivated you are to do anything that would break yourself out of the depression. I have a set of warning points I watch, for now, to call for help before I get to the level of sitting in a dark-room ignoring the world. If I get to that level things are bad. Maybe sometime I will be able to write about the time I spent at that point in my life, but perhaps not.