Well snakes can stress out so wouldn't that be connected to emotion? Something like fear, put a snake on the ground and stand over it, I've never seen a snake remain calm with a person doing that. I know my Blood python will freak out if I do that and he will get very defensive and start hissing.
Perhaps a better example might be handling a snake for too long. Mine can get squirmy and tense when I handle him for long periods of time so that could be anxiety.
Or would that be related to something else?