To cry over spilled milk is to remain upset about a past loss. When milk has been spilled, it is wasted and cannot be used. There is no reason to keep complaining over the loss. Note that either of the words spilled or spilt can be used.
-I can't believe we're over! You're not even going to fight for me?
-stop crying over spilled milk, we're done...you really bruised my ego.
-oh, cry me a river!
Crying over spilled milk is when someone bitches about something so stupid and pathetic
Terry: Oh no, i left my penny at my grandfather's house! WE HAVE TO GO GET IT!, OMG HES NOT ANSWERING HIS DOOR, LIFE AS WE KNOW IT IS OVVEVERR
Me:Ah pipe down you loud whiny dick-in-a-bucket, Quit crying over spilled milk; the old fuck isnt even home, Plus you could find a penny on the ground, dumb twat