Got to the bottom of my recent dire mood with help from elflet, asker of useful questions*. Funny how, once the exact feeling has pinned down, the reasons magically emerge from the background noise, but the job cannot be done in reverse order (too much background noise).
Anyway, I am civilized and optimistic once more (even if I did dream of talking to xthread, which turned into one of my complicated-journey dreams, this through three levels of an underground bank, sort of like the malls in Toronto.) And the birds in my soul are singing again. Even if they do sound remarkably like David Byrne.
*The useful question, which probably owes much to Cherie Huber, is approximately "Consider depression as a refusal to feel something. What are you refusing to feel?"