Maybe I'll try this.
Today instead of running, or biking, or any kind of training, I cleaned house ("cleaned RV"), did 3 loads of laundry, went grocery shopping, and mailed my last Christmas present, which will never, never make it before Christmas.
I feel much better today.
I should know not to try to run two days in a row. I find over and over I can't do that. That's why I do so much of my marathon training on a bike. Because I can't run on consecutive days. I shouldn't have tried to run long yesterday after running even moderately (4 miles) the day before. I know I can't do that.
Now that the rest of you know, too, don't let me try that again.