Choosing the right nap
Not all naps are equal. A 20-minute power nap keeps you in light sleep, so you wake quickly and feel sharper almost immediately. A 30-minute recovery nap digs a little deeper and helps repay lost sleep, at the cost of possible brief grogginess. A 90-minute full-cycle nap takes you through an entire sleep cycle including REM, which can boost creativity and memory, and because you wake at the cycle's end, you avoid sleep inertia.
The danger zone is in between: naps of 45–75 minutes tend to end during deep sleep and can leave you groggier than before. If you can't spare 90 minutes, keep it short.