Stop Malding
People would say it's "mad" and "balding"; mad and getting bald because your always mad. But it's more to being a piss baby. So the general definition is being a piss baby. Stop malding = Stop being a piss baby.
*You and someone just finished a fight in discord (chatting app) and you've realized that you're the one who's wrong, so you decide to leave (because embarrassed)*
The person who you fought: Lol, stop malding.
The person who you fought: Lol, stop malding.