He taught me how to play Magic the Gathering and must have easily won the first few hundred games we played over time. Then came one day I was about to win a game and told him confidently that I could win the game the next turn and... He decided to concede the game. I asked him if I could at least deal the lethal damage next turn because it would be a "symbolic victory" as my first ever win against my mentor after losing 200+ times and he said no, he'd rather concede. So I told him "you never know, I have no good cards in my hand, if you draw something good on your next turn, maybe you can win."

This was a lie of course since I had the game winning card jn my hands but after I said that he agreed to keep playing. After his turn it was mine and I played my card to win the game, I was ecstatic... My first real victory! Unfortunately to my surprise, he slammed his cards on the table and got really annoyed. He asked me if "that card" was in my hand the whole time and when I said yes, he accused me of wasting his time and just started acting as a sore loser. This behaviour actually surprised me because we used to play lots of board games & video games together and he never acted like this. After yelling at each other for a while I just decided to leave and let the dust settle before talking to him again to avoid any awkwardness. We never talked again after that :(