Writers block: when I get it, it's because my subconscious...

Writers block: when I get it, it's because my subconscious spotted that I'd make a huge structural mistake in constructing a novel before my conscious mind became aware of it, and threw on the brakes. So I've learned not to sweat it: take two days off, then back up a chapter, read through, and try to work out why I'm suddenly uneasy about continuing.