playing out games
A Queen or Rook down is an insurmountable material deficit unless there is immediate compensation (like a mating attack). If you want to learn how to cash in when you're up, play on. But the time spent in the lost cause might be better spent in a new game.
At the very least, there's a whole economy behind value per unit time in learning chess by playing in a losing situation that's more complicated than either a blanket "play on" or "resign" really solves. The right choice not only depends on the game and the players' skills, but what they want to get out of playing.
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