Woke up on the wrong side of the bed

alt: got up on the wrong side of the bed. (past tense)
an expression that is typically used to describe a grumpy or irritable person, especially when the reason for their unhappiness is unknown.

it can also be used to describe when somebody wakes up in a bad mood which then lasts all day, possibly because they didn’t get enough sleep or had an unpleasant dream the night before.

the phrase dates back to ancient rome, where it was considered bad luck to get out of bed from the left side, which itself originated in a very old superst-tion saying that everything related to the left-hand side was inherently unlucky. the modern english expression reflects that myth with a tongue-in-cheek play on words, suggesting that a grouchy person must have gotten out of bed on the “wrong” side, as opposed to the “right” side.
“what’s with wendy? she seems annoyed about something.”
“i don’t know, maybe she got up on the wrong side of the bed today.”
– – – – –
“you’re acting like real jerk!”
“sorry, i just woke up on the wrong side of the bed this morning. i’m in a bad mood, but it’s not your fault.”