I always find this to be the case with my sister and me. Over the entire course of our Arkham Horror boardgaming history, my sister has been racking up successes with every skill check, boldly attacking powerful monsters and destroying them with ease. Me? It's the exact opposite, as the dice defies me every time I pick it up.
She can even make dice fail at will! There was an encounter in the Witch House: Make a Lore (-1) check (I think). On a success, gain a spell. On a failure, gain two clue tokens but you are delayed. Since she was the spy, and wanted to accomplish her personal story, she wanted to fail. Roll 4 dice, and failed, just like she wanted! After that, things continued as normal (me messing up, her racking up successes).
Which makes me wonder: are the dice jinxed? And is there a way to magically control the dice like my sister?
Perhaps you guys could give me some words of wisdom, or share stories similar to this one.
If you lose, it shall mock you as you despair. If you win? It shall be watching and waiting for a chance to crush you once and for all...

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Only this time I only had one ally left anyway, so it didn't really matter. The funny thing was that this was the ally that you can sacrifice to negate the Ancient One's attack for one turn