That was last night for me....GRR!..
Last night there was NOTHING that I could play right. I usually warm up with scales and open chords but even those..
After about 15 mintues of running up hill in mud, I said screw this and put the guitar down, and walked away.

I came back an hour later (because I felt guilty not practicing) and worked on Hammer Ons and Pull offs and that seemed to click a little better.

Its wierd but there are some days where I am Alex Lifeson and seem to play like a rock god or just get something that I have been struggling with and I run around the house doing a victory lap, arms in the air wooping it up (I really do! My wife and girls roll their eyes which encourages me MORE! ;-) )

But then there are other days where I can't tell G-strings apart!

I bet a ton of it is psychological or maybe I am just pyscho...who knows?!