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.
If you try to draw the Master Sword from its pedestal, you'll find that it starts to drain your health. This is its way of measuring your strength to see if you're worthy to wield it. Before you can lay claim to the Master Sword in The Legend of Zelda: Breath of the Wild you'll need to have at least 13 hearts. Once you have 13 hearts, you can go attempt to pull the Master Sword from its resting place in front of the Great Deku Tree and right before your 13th heart runs out Link will pull it free.