Here's my only complaint, to fellow people who work a regular job or startup AND a side project: don't chunk all of your work into the weekend. Try to at least see your code every day, otherwise it's like coming back from a week-long vacation and not remembering your code very well. Ever stare into the sun and try to get around in a dark room? It's like that.
This past week has been particularly bad because we're doing a push on the product and I've had to do some hiring, but usually I'll try and at the very least look over my code every night so I can keep it fresh in my mind (which keeps my productivity just as high).
And wow, I can relate to this:
"All the engineers kept notebooks, of course. Blogs. They'd write frustrated entries, only to have massive elated breakthroughs the following day."
As for the recommendation to learn native JS: I suggest you instead take the route of learning jQuery. Say goodbye to cross-domain, cross-browser, xmlhttprequest issues. Selectors, manipulation, AJAX, traversing, CSS, effects, it's all there and it works really well.