Quick power naps, which may be a secret to live a long, happy life, can make you more alert. Napping during the day is especially beneficial to people who work in shift, according to Dr. Doghramji. The best kind of nap is 20-30 minutes long and taken around the same time during the day, he adds. Avoid extended naps after 4 p.m. because they can mess with your ability to fall asleep later.