Wake up on the Wrong Side of the Bed

You use the phrase ‘Wake up on the Wrong Side of the Bed’ to indicate that someone
is in a bad mood.

Example of use: “Try not to wake up on the wrong side of the bed tomorrow. You’re awfully grouchy today!”

Interesting fact

The origin of the expression ‘wake up on the wrong side of the bed’ is thought to come from ancient Rome. Romans were very careful always to get up on the correct side of the bed to ensure that good luck would follow them through their days. If they got up “left foot forward” or “on the wrong side of the bed,” they believed that they would be unlucky.