1. Don’t Cut Your Nails at Night
yoru ni tsume wo kitte wa ikenai
夜に爪を切っては行けない/よるにつめをきってはいけない
In the past there was no electricity to light the streets or your home at night. People believed evil spirits, akuryou (悪霊/あくりょう), would come around when evening approached.
It was believed that cutting tools (like fingernail clippers) had spiritual power, known as reiryoku (霊力/れいりょく) in Japanese, that could divert evil. At the same time, cutting instruments created a gap in whatever they cut which allowed evil spirits to enter through the gap if it was used at night. Although this saying isn’t so popular in modern time, it might be a good idea to keep the light on next time you cut your nails.