the other shoe

The common expression “waiting for the other shoe to drop” has always puzzled me. First of all, it implies that there is indeed another shoe when there very well might not be one. Secondly, I find it to be inherently pessimistic, paranoid, and the foundation for a self-fulfilling prophecy. Like even when I’m happy, I ought to be expecting that other shoe to come along and ruin things?

Perhaps, though, another person may find comfort in that expression. Perhaps that person is prepared for anything to come her way, including that other shoe. Perhaps that person is a realist who deeply understands metaphoric shoes more than most people.

I don’t know. It still puzzles me.

What does that expression mean to you?