One funny thing about teaching, even after 20 years, is how each class goes differently. So you never quite entirely get past the highs and lows. I've been doing this intensive-schedule tax policy class at Singapore, where you go for 3-1/4 hours (with only short breaks) 4 days in a row. Then, after a long weekend, four more days in a row.
I thought my first two classes went well. Fired up for the first one, sluggish start then strong recovery for the second. But today, for the third class, which (like the others) started at 12 pm local time, I decided at about 8 this morning that I didn't like my layout for the first third of the class. So I spent what should have been my usual morning prep time revising that portion. Bad idea. I showed up for class not having done adequate day-of-class review of the last two-thirds. Result, even though I know the material quite well: much harder to explain things coherently and clearly, and to keep in mind what sorts of threads to pick up and which to avoid.
Oh well. Tomorrow is another day.
UPDATE: Well, I feel it's been going better recently.