In the writer's group this week several members had "bad" weeks. They described their frustration, their various problems. The funny thing was that even these bad weeks were pretty good: everyone made some progress; one "bad week" involved an article being accepted. In another case, someone made progress on a writing progress, but less than what they had wanted to do.
With enough "bad weeks" like this, these writers will be extremely productive in the long run. Long term progress will take place over many weeks of varying quality, some bad, some mediocre, and some great. A bad week, then, is not even a bad thing. Nobody cares about how little you did during your worst two or three weeks of the year.