Napping is great for when you're feeling tired or stressed and need a quick energy boost. According to experts, you should only nap for 10 to 20 minutes a day. Napping for less than 10 minutes won't provide you with the stimulating effects of napping. While napping for over 20 minutes could cause you to fall into a deep sleep, which will make it more difficult to wake up. If you wish to take a nap during the day then it should be between 2 and 4 PM. This is because our body temperature decreases during this time, similar to how it decreases at night. People that suffer from insomnia should never nap, as it will make it more difficult for you to fall asleep at night.