I did the third run this past Friday (the 13th) and it was the hardest run of the week. Several times I nearly gave up and walked, but I'm glad I didn't, as just a few seconds after I was tempted to quit Laura came on and said it's time to slow down to a walk. By the end of the second 3 minute run I was really struggling, but persevered and walked a third lap around the housing estate.
(more detailed blog: tinyurl.com/blwzqwl)
I'm not sure what made the third run so difficult. It was a nice cool morning, it was raining but not too much. Maybe just an "off" day?