Tetris is not just a fun diversion, but also has remarkable trauma-fighting properties. Playing Tetris within 24 hours of a traumatic event has been found to significantly reduce the likelihood of intrusive memories, and the game has also been used as a behavioural intervention for treating established PTSD.
It is not yet clear whether these properties are specific to Tetris or would apply to a broader class of games or activities (though the original poster has heard anecdotal reports of Solitaire serving this purpose, and trivia not working).