Se lever du pied gauche

Literally: To get up on the left foot

Example: “Ne lui parle pas maintenant, il s'est levé du pied gauche ce matin.” — Don't talk to him right now; he got up on the wrong side of the bed this morning.

English equivalent: To get up on the wrong side of the bed

Origin: The left side has been the unlucky one in European tradition since antiquity: Latin sinister meant both "left" and "ill-omened," the sense that survives in English. French also had the older être sur le pied gauche, which Littré explains as a fencing term for a fighting stance and finds in the 17th-century memoirs of Cardinal de Retz, of people ready for a quarrel; Saint-Simon used le pied gauche for an awkward, uncomfortable position. Getting out of bed left foot first combines both ideas: the day starts on the wrong footing, and in a bad temper.