Some days you just don't have it, mentally or physically. I jogged 3 miles with Sumo intending to tackle some intervals but never even started. My normal routine is to drive the 1 mile distance to the trail and start from there when I have Sumo. Feeling the way I did, I happened to have my mountain bike in back and did 6 x 800 repeats with it instead. My quads were burning, my cardio was taxed, and I felt good doing it, something that would not have experienced had I been running.
Triathletes have shown us that cycling can improve running. If I lived in a warmer climate, I'd be doing this more often.
3 miles total- so what?