Don't throw the towel in on your day too quickly! Today I woke up, Day 4, cardio planned, feeling less than great. I had a bellyache and felt grumpy and altogether unwell. I am tired from the past 3 days of working out, but I know that tomorrow is a rest day because of my busy schedule, so it's either bust out the cardio or take 2 rest days in a row.
I manage to get motivated to climb on the stationary cycle with no aspiration other than loosening up and getting SOMETHING done. 50 minutes later I completed a great cardio sweat session, clocked some minutes for the week and set myself up for a well deserved rest day tomorrow. Oh ya, and my belly ache was gone; and I wasn't grumpy anymore :) Go figure.