Day to day differences

My plan for the off days was to do 30 minutes of strength exercises and stretching.  I had planned to do it all in the morning, but I decided that an extra 45 minutes of sleep sounded better so I decided I'd do it all after work.  I have noticed a significant difference in my energy level today.  On running days, I feel energized, for the most part, all day.  Today I'm yawning and a little listless.  It really is amazing the difference that the exercise can make in your day.  I'm actually looking forward to the day in the near future that I'm good to run more than 3 days a week.  Even if it's just the 1k jog to the end of the street and back.