It turns out, my Fitbit doesn't make me sad, but the numbers I get when traveling sometimes do. Despite a 3.5 km walk around Springfield yesterday, it was the second day in a row and the 4th in 10 days for which I missed my 10,000-step, 10 km goal.
On the other hand, last night I got almost 9 hours of sleep (according to my Fitbit), through several trains and a thunderstorm.
Yes, there was a thunderstorm in December in central Illinois. That's just weird. And in future, probably a lot more common.