You can not think about the game. If you do then you have to say (audibly) "I lost."
This outburst may cause anyone in the vicinity to start swearing because you reminded them of The Game and therefore they lose. The only way to win The Game is to never know about it.
Boy:*thinks about The Game* "Crap, I lost The Game!"
Girl: "shut up!"
Girl: "what did you lose?"
*boy precedes to tell her about The Game*