måla fan på väggen

Swedish edit

Literally, "paint the Devil on the wall".

to assume the worst is going to happen
A to B: "I am going to forget what to say and everyone is going to laugh at me."

B to A: "Do not paint the devil on the wall."
to present a situation as being worse than it actually is
Hon målade verkligen fan på väggen när hon kallade sin partikamrat fascist.
She really went too far when she called her fellow party member a fascist.