An unplanned rest day-today

I didn't run today because I took an unplanned rest-day. I felt fine after my run on Thursday, but during the afternoon I noticed my throat was getting a slight rough feeling. Then, during the evening my nose started running, and it ran all day Friday and all day today, although my throat feels fine. When I woke up this morning, I felt fine, and I thought I would run through my cold. However, while doing my sit ups I could tell my energy level was low, and I aborted the sit ups and changed into my regular clothes. I've just moped around today and haven't done much but talk to my five grand kids who are visiting and watch a couple of DVDs with them.