"Wrong side of the bed." What does that even mean?

How is it possible to wake up on the wrong side of the bed? And even if you happen to wake up on the other side of the bed, why does that negatively affect your disposition for the day? Waking this morning in a grouchy mood led me to search for the origin of this phrase.

"The saying stemmed from the early expression 'Left foot forward'. The supposedly sinister nature of the left is reflected in many English superstitions and expressions, such as the belief that it is unlucky to put your left shoe first, or to walk into a house left foot first. The Romans, especially Augustus Caesar, were very careful that they got up on the right side of the bed, but there is no evidence that they were less grouchy than anyone else." From "Encyclopedia of Word and Phrase Origins" by Robert Hendrickson (Facts on File, New York, 1997).

So there you have it. Getting up on the wrong side of the bed stems from a superstition that the left side of the bed was bad luck. Therefore, waking up in a sour state has little to do with what side of the bed you awoke in but rather something else entirely.

Since I could not pinpoint the deeper cause to my irritation at 6am, I concluded that there was no antecedent to my behavior and no evidence that it should last all day. So I went to school, had a blast, left school, had a blast, and am now reviewing the day in slow motion. I had a great day in spite of the fact that I woke up on the "wrong side of the bed".