I like to call them Glitch days. For me it seems to happen on a trick that I have on lock usually. For men anyway a HUGE part of it is Frustration. I start to get pissed off at my riding, start over thinning everything, then I cannot land anything. Like the Hammer Says usually its over the next set once I clear my head.
Trick Glitch is even more frustrating to me, where you have a trick on lock, you can do it in your sleep, then you crash on it once, and its gone for the whole set or longer. Last Fall it was a Crow Mobe. A trick I have had on lock for year, suddenly one set I went out the front and got blasted pretty good. Pissed off of course I got right back up and tried the trick first hit again, same shiat out the front. Then I must have tried it 50 more times in 3 sets crashing like I had never done the trick before. Took the next day off and then I was suddenly landing it again a few days later.
Most of us backyard warriors demand perfection in our riding. It doesn't take much to get us pissed off then everything starts falling apart in our riding. Best thing to do is to just go out and goof off remember why you love the sport.