I was wondering what the "eek" could be about, and then it occurred to me: you hate to be embarrassed by your department chair getting down on the floor, hugging your ankles, smooching your feet, and crying over and over, "We're not worthy! We're not worthy!"
Oh, Bartleby, would that such were possible!
The chair is one of the nicest people I've met in a long time and word through the grapevine is that while he won't be casual or perfunctory in his evaluation, I shouldn't lose sleep over it.
At the same time, said chair is best described as "inscrutable." In other words, he's hard to read. Therein lies the source of my neurosis. Naturally, he has opted to attend the class about which I am least confident. On the other hand, the students (to my astonishment and delight) do seem to not only pay attention, but to retain the material, sometimes better than I.