So yesterday I rode the new bike up to Meguro and back to teach a lesson. The lesson is that riding 17 miles in 104-degree heat is only a good idea if you have lots of water handy.
Today my Monday lesson shifted to Tuesday, so I had nothing to do. I decided, possibly quite wisely, to avoid riding, and instead walked down to the station to pick up a saddle pad and a water-bottle holder. (Thrilling stuff, this.) I also decided to get some cycling clothes and found a shirt and shorts in the sporting goods shop on sale.
On the walk home, I remembered another sporting goods shop along the way, sort of, and stopped there and got another shirt and shorts. Good prices, and I'll be back there.
The upshot was, instead of riding 20 miles, I wound up walking 6.5. Some rest.