I was riding a smallish bike very fast and easily through the streets of my home town. I had been to my piano lesson and was heading toward my voice lesson, but then I realized I had to turn around and go the other direction, North rather than South. I also realized I had left my music book at the piano lesson so I wouldn't be able to practice for a week.
The bicycle was technically too small for me, but still comfortable; I had to pedal very fast, but there was no sense of effort. It was dark, and there was no other traffic on the streets.
Literally, of course, there was no exertion in riding this bike, since I was lying in bed dreaming. Certain things have no reality in a dream: I cannot taste food, nor do I feel pain when beaten up in a dream. Yet other things are real, like the engagement of the sense of sight, or arousal, or the psychological reality of dread or wish fulfillment.