i'd suspect the drop in STA times are mostly mental but could also be caused by other factors like changing eating habits. Once the times drop, mentally it's even harder to get back as more stress is added...
I had ups and downs too, just took a few days off doing tables and tried to have a good ol' relaxed STA next time. Suprise, suprise, sometimes it works the other way too...after a line up of bad results, one can suddenly and "without training" get better times than before! Not big improvements though, i'm still waiting for the big break to move from 5 to... 8 minutes
