"I think the vast majority of people who need a nap during the work day simply don't get enough sleep at night."
During tax season, I work every day: morning, afternoon, and evening; 14-18 hr workdays are the norm. I used to be working so late at my desk, I'd start to nod off. I'd shake out of it, and drive on, but I began to notice after that point I was much less efficient, and much more prone to error, so I created a new rule: If I nod off, even for a moment, that' s the end of the day, and that's when I go to bed. I noticed almost immediately my error rate dropped, and I became much more efficient during the rest of the day.
Over the years, that rule has morphed, particularly since my heart attack: Now, if I hit a wall at any time during the day, and either lose focus or start to f^ck around, it's time for a nap. I realize fully, when I wake up, it's right back to the desk, but it's helped with efficiency and focus so much, I've made it a work rule, for both myself and my assistants:
Sometimes, the most efficient thing you can do at work is take a nap.