Everyone has those days when you can't shoot for shit

I've been playing piano for nearly twenty years now. Every once in a while, I get into a kind of slump where my piano playing doesn't go well at all. Luckily, these times happen rarely.
Lately, though, my playing has sucked, so I guess it's one of those times. My concentration is off, my fingers are clumsy, my expressiveness is shot, and I'm not having any fun. It's frustrating. However, I've learned the the best way to deal with it is to just play right through. Keep up with the daily practicing, don't give up, relax, and don't worry about it. Everything will come right soon enough.