Yep happens to me quite a bit. What do I do I put it down and go for a ride on the horse,or motorcycle or go fishing. Some days you just get brain fade. You haven’t lost it ,it’s just taking a day or two off. Stay safe and good luck.
Of course it's happened to me and to others. Why? Who knows. Maybe something happening in your life is causing you to be unable to concentrate, maybe it's just one of those things that none of us can understand, but it happens. Don't let it bother you. Try again tomorrow and maybe you'll find that you can actually play better than you did the day or two before.
It's a matter of focus for me sometimes, and a matter of physical condition other times.
If I try to play the banjo after doing something strenuous with my hands, the hand fatigue can make things difficult. If I can't get focused enough to get into the zone where my mind is relaxed and is happily concentrating on just my banjo, I won't be happy with what I'm playing.
As was mentioned in another post, I think regularity really helps too. There are always going to be days when everything clicks and days when it doesn't. With enough time in the exercise, I expect more of the first will happen and less of the second.
I haven't ever been that regular, though. I tend to practice in fits and spurts, and I'll either quit too soon or practice too long. The second wears me out, but I always get more satisfaction when I practice for several hours non-stop. regards, stanger
I don't think there is anything a person can do except take a short nap and put a little more effort into concentration when they start playing. Our physical and mental state affect our concentration, and that has an impact on our playing.