I can tell. When I start to get a little mean or snarky, it's time to hang it up for the night. I started a mini marathon session about three hours ago... maybe a little more... and I was reading good essay after good essay. Now, however, they seem trite and hokey and contrived. What has changed? Not the students.
So... I'll put away the stylus*, get some sleep, and plug away again tomorrow. I'll probably revisit the last couple of essays I read tonight to make sure I wasn't too hard on them.
The good news is that I'm WAY more than half way done with this big batch.
*I have had some fun grading on "my" iPad (it really belongs to the college, but I still play Plants vs. Zombies on it from time to time... don't tell) with iAnnotate. That overpriced little app allows me to customize almost infinitely and create shortcut after shortcut. Pretty fun, really. And actually, for what it can do, the app isn't overpriced. Especially after I learned recently that it has come down in price since I got it. So... there you go.