Certainly I'm usually anticipating some crap or other might happen to me. It's like hyper-vigilance, only not so intense. Just a vague feeling of "it's been a good day so far, I wonder how long it'll be before some bastard spoils it." On most days nothing very bad happens, but sometimes it does. Like a feeling of sitting on a time bomb.
I think you mean "waiting for the other shoe to drop."