Many believe that if all of the candles on a birthday cake are blown out with one breath, while making a silent wish, the wish will come true.
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It's bad luck to leave a house through a different door than the one used to come into it.
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An acorn should be carried to bring luck and ensure a long life.
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When you speak of bad luck, it is said that one should always knock on wood. Also knocking when speaking of good luck apparently helps with having good luck. This is an old Celtic tradition related to belief of wood spirits.
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A single magpie is considered a sign of bad luck. A Guide to the Scientific Knowledge of Things Familiar recites an old proverb concerning the incidence of bad weather when magpies forage alone and a possible scientific explanation for this.
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There are numerous sailors' superstitions, such as: it is considered bad luck for a ship to set sail on a Friday, to bring anything blue aboard, to stick a knife into the deck, to leave a hatch cover upside-down, to say "pig", or to eat walnuts aboard.
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Opening an umbrella indoors is said to result in 21 days of bad luck. Some traditions hold that it is only bad luck if the umbrella is placed over the head of someone while indoors.
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Placing a hat on the bed is, apparently, bad luck. (South Carolina)
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