Horseshoes are considered good luck while black cats and the number 13 are considered bad luck. Not many people take these superstitions seriously these days, but the associations have stuck around.
To me, horseshoes are a bit different to the other two because "good luck" is not the first thing I think about when I hear the word "horseshoe". "Black cat" and "number 13" have stronger connections with "unlucky" than “horseshoe” has "with lucky" (in my mind).
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