What puts a knot in your stomach?

Getting the 'knot in the stomach' feeling on the way in to work, and the 'angry red anthill' energy that greets me like a slap in the face when I first step over the threshold.
 
When I worked at a nursing home, I had clowns who came in to do "laugh" therapy. Turned out most of my residents where fleeing in fright! Had to stop that even tho they were nice people who just wanted to volunteer. It appears a lot more people than thought do NOT care for clowns!
Here's one of my favorite clown scenes in a movie!