Thursday session - DNF, need a rest day

I knew when the alarm went off this morning that today was going to be a struggle. Convinced myself to get out of bed and run up to North Head. Feeling like this is not unusual before a hard session, but today in particular was quite different. My legs felt heavy and lethargic, and the actual effort of warming up felt harder. Started the first 400m, pace was slightly off, but when I started the float I knew I didn't have it in me today. Unconvinced, I walked back to the start and gave it another shot. Same thing, 400m hard then couldn't run the float properly. Walked back to the start, and jogged straight back home. I very much hate pulling the pin on training! I think a mistake in my recent week was running Sunday too fast in the heat, especially the day after racing 10km. Again, I didn't feel great on Tuesday, but I think the heat really masked any lingering fatigue from the weekend. Today it was obvious. Always get a bit paranoid due to my past of bouts of lingering fatigue, but hopefully I can nip this quite easily via no running or training for the rest of today and tomorrow. Plan is to run a threshold session at Centennial Park (instead of Mt. Steele hill repeats) with the others who are racing Melbourne in 10 days time.