To be at sixes and sevens is to be all confused, in complete disorder. As in “Today I overslept, forgot my diary, my phone is broken…I don’t know what’s going on! I’m all at 6s and 7s! Aargh!” or “The Barça defence was all at 6s and 7s, so Espanyol easily scored three goals.”
The phrase even appears in the song Don’t Cry For Me, Argentina, from the musical Evita! Nobody really knows where it originated.