i'm so timid that i will not usually respond to a knock, being reasonably sure that i have locked the door. forcing them to try to open it. so far i've never mistakenly left it unlocked.
My problem is that I'm just jumpy by nature. Any sudden noise freaks me the hell out no matter what I'm doing. It's never fun but it's just that much more unpleasant if you're pooping at the time.
It would be just my luck to have a heart attack while pinching a loaf.