Not enough sleep or disruptions to the sleep-wake cycle (such as those that may occur with shift work or travelling to a different time zone) cause the physiological state known as fatigue. Staying awake for 24 hours leads to a reduced hand-to-eye coordination that is similar to having a blood alcohol content of 0.1.
There are 13 hearts in a standard 52 card deck. There are also 13 diamonds, 13 spades and 13 clubs.
There are six cards in the Tarot deck featuring this number: the four suited cards (Three of Swords, Wands, Pentacles and Cups) and two cards from the Tarot's Major Arcana: The Empress (card number three) and Death (card number thirteen).