I attended a Thanksgiving dinner several years ago where the hostess, without warning family and friends, broke with tradition and served salmon instead of turkey, roasted potatoes instead of mashed, raspberry coulis instead of cranberry sauce and … you get the idea.

While a few guests mustered the politesse to say the meal was “something else,” most reacted with undisguised dismay. Some seethed. Others sulked. One young guest actually cried. No one had seconds.

It wasn’t that the meal itself was bad. In fact, the meal was outstanding. The problem was that it wasn’t the meal everyone was expecting.

When there are discrepancies between expectations and reality, all kinds of distress signals go off in the brain. It doesn’t matter if it’s a holiday ritual or more mundane habit like how you tie your shoes; if you can’t do it the way you normally do it, you’re biologically engineered to get upset.