"Don't go to bed earlier than usual. You should follow the same schedule every night, including weekends, so you don't mess with your circadian clock and disrupt your regular sleep rhythm. Take a ten- to 15-minute snooze (your car will do if you're far from home), then keep shopping. That's all you need to rejuvenate and get through the rest of the day. Sleeping for 60 minutes would leave you groggy, and since 90 minutes is typically a full REM cycle, napping for that long would likely make it hard to fall asleep at your normal bedtime."—James B. Maas, PhD, author of Power Sleep, former chair of psychology at Cornell University, and coiner of the term "power nap"