I tried Week 6 day 3 two days ago and had to walk for a minute at the 20 minute mark. Cardio felt OK but my legs were so tired!
I got home at 10 this evening, felt a bit tired, but decided to go out for a late run and have another crack at it. I did it and actually had enough in me to push the last minute - even taking the uber hill route I avoided last time! Really pleased with it. I also seem to prefer running when it's late, dark and quiet (not everyone's cup of tea, I know.)
I think what affected my first attempt was lack of sleep in the preceding days and cutting calories. I perhaps cut too many, so the last few day's I've been resting and fueling up. It seemed to make a big difference!
The app tells me that I'm now officially a runner :D.