A term from a classic MTG article, saying that similar matchups are won and lost most frequently because of role misassignment. It is generally correct for one person to be the aggressor (the beatdown) and the other to be the control deck. This is true even if both decks are aggro, or both are control. The aggro deck on the draw might just want to trade one-for-one and control the board, while the control mirror player has to recognize whose deck can go the latest.
Not sure how this generalizes to life but it is a concept I quite like.