Aborted my run after a mile

My wakeup heart rate was 56, higher than it has been the past few days. I started my run in the mid-afternoon. The temperature was in the low 40s (F). As soon as I started running, I could tell I was tired, so when I reached the 1/2 mile marker, I turned back. I only had 5 hours sleep Saturday night. I picked up about 45 minutes with short naps during the afternoon, and I picked up another half an hour last night when I got a good 7 1/2 hours of sleep. By aborting the run today, I'm giving my body extra rest, and hopefully I'll do better on Wednesday.