Dealing with frustration after a bad run in blackjack involves acknowledging and accepting your feelings rather than suppressing them. It's important to take a step back and reflect on the experience without letting emotions dictate your next moves. Engaging in activities outside of the game can help you reset your mindset, allowing for a clearer perspective. Focus on the long-term aspects of your gameplay rather than short-term setbacks, reminding yourself that ups and downs are part of the game.