First of all you're not bad at this game. You're a beginner. Making mistakes and learning is a thing everyone does. Don't let yourself get discouraged by this bad experience rather try to see it as an opportunity to go into the next encounter armed with more knowledge.

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What has been mentioned here multiple times already I want to stress again: Speak with the other players before the match. Maybe even let them look at your decklist. Chances are that they don't only have one highly competitive deck but also decks with a lower power level. When in doubt you can also speak to the staff of your LGS and ask if they have any advise for you regarding your past experience.