Feel groggy? A good nap should only be about 15 to 30 minutes. Any longer and your body starts to fall into something called delta sleep.

Delta sleep is that deep sleep that—when interrupted—can make you feel more tired than when you started. But with just a half hour or less, you start to feel more rested and alert, and can even increase your ability to make decisions and notice details.

The reason is that a good nap gives your nervous system time to recharge, which improves your mood and alertness when you awake.

So take scheduled catnaps to recharge. You eyes will be brighter and more beautiful, to boot!