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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Placing keys on a table is considered unlucky. (Sweden)
3
The superstitious symbolism of a black cat crossing one's path is dependent upon culture: some cultures consider this a sign of impending bad luck, while some cultures consider this a sign of impending good luck.
75
At times, a horseshoe may be found above doorways. When positioned like a regular 'U' it supposedly collects luck. However, when it is positioned like an upside-down 'U' the luck supposedly drains.
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Once a wedding ring has been placed on the finger, it is considered bad luck to remove it.
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Collect seven or nine different flowers on midsummer eve and place them under your pillow and it is said that you will dream of your future spouse. (Sweden)
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If you catch a falling leaf on the first day of autumn you will not catch a cold all winter.
394
Two people breaking a wishbone is said to lead to good luck for the person with the larger piece.
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