Do you work backwards from those great last lines of yours?

Actually, I didn’t think this one was that great — it struck me as a tad awkward. I spent a lot of time trying to improve it, and finally gave up.

But to answer your question: no. The last line is typically the next-to-last thing I write in any post or poem. The very last thing to go on is the title.

But to answer your question again: yes. Quite often, after coming up with a good ending and title, I’ll rework the beginning a bit to harmonize with them. (I don’t think that happened here, though.)