hey HH, this is funny but i had the same thing happen to me about a half hour ago!
I got my squat and bench reps but missed 2 reps on the last set of chins, lol!
i had a pretty rough day at work, moving and setting 30lb blocks for about 4 hours (256 of them!!) so i felt a bit spent and my hands were really tired.
anyway my point is (yeah i have one, lol!) not to let it get ya down cuz we all have "off" days!