anti-jinx

A practice often used at sporting events.

It's an attempt to jinx your opponent by openly calling the match in their favor or by predicting doom and failure for your own team, saving face in case you lose, whilst simultaneously allowing you to be incredibly smug in victory and thereby fulfilling the anti-jinx.

American fan - Bro, it's obvious, Canada is totally winning this!
Canadian friend - Fuck off Matt, everybody knows what you're doing, stop trying to anti-jinx it.