It's no use crying over spilt milk

It's no use crying over spilt milk or  Don't cry over spilt milk.
Prov. Do not be upset about making a mistake, since you cannot change that now. 

• I know you don't like your new haircut, but you can't change it now. It's no use crying over spilt milk. 
• OK, so you broke the drill I lent you. Don't cry over spilt milk.