Definition of the day: Because, you know, I'm in that kind of mood

mea culpa

My fault, due to my error; my bad.

The origin of the expression is from a traditional prayer in the Mass of the Roman Catholic Church known as Confiteor (Latin for "I confess"), in which the individual recognizes his or her flaws before God.

The text in Latin is:
Confiteor Deo omnipotenti,beatæ Mariæ semper Virgini,beato Michæli Archangelo,beato Ioanni Baptistæ,sanctis Apostolis Petro et Paulo,omnibus Sanctis, et vobis, fratres (et tibi pater),quia peccavinimis cogitatione, verbo et opere:mea culpa,mea culpa,mea maxima culpa.Ideo precor beatam Mariamsemper Virginem,beatum Michælem Archangelum,beatum Ioannem Baptistam,sanctos Apostolos Petrum et Paulum,omnes Sanctos, et vos, fratres (et te, pater),orare pro me ad Dominum Deum nostrum.Amen.

This translates into English as:
I confess to Almighty God,to blessed Mary ever Virgin,to blessed Michael the Archangel,to blessed John the Baptist,to the holy Apostles Peter and Paul,to all the Saints and to you, brothers (and to you Father),that I have sinned exceedingly,in thought, word and deed:through my fault,through my fault,through my most grievous fault.Therefore I beseech the blessed Mary,ever Virgin,blessed Michael the Archangel,blessed John the Baptist,the holy Apostles Peter and Paul,all the Saints, and you, brothers (and you Father),to pray to the Lord our God for me.Amen.