A few months ago, there was a lot of discussion and a bit of vitriol about Sheryl Sandberg, the COO of Facebook, and her habit of leaving the office at 5:30 pm in order to have dinner with her family. Much of the discussion has focused on the difficulty of women in executive positions to balance work and life, etc.

For me, the issue is that Ms. Sandberg is puncturing that greatest of American entrepreneurial and corporate myths:

To work hard is to work long hours.

The defenders of this myth, all of whom are seeking to justify their required 80+ hours work week are shocked, truly shocked, that someone can do an executive job and still leave the office at 5:30 pm. They just do not believe it.

But, of course, equating hard work with long hours is a canard; a very dangerous (and potentially health-damaging) lie that many of us tell ourselves. Working hard is not about working long hours. Rather, working hard is a matter of doing the hard and important work when you are at work.

If you look at published statistics on productivity in the US compared to a current golden child in the world economy, Germany, you will note that the US leads in GDP (gross domestic product) per person, but trails badly in GDP per hour worked. By working longer, we are making up for our inability to work hard and work effectively when we are on the job.

Let me share a personal anecdote about my experience working in Germany two decades ago that drives home the ideal of work hard, not long.

One year out of business school, I was transferred to a German subsidiary to work in their finance and strategic planning department. Their work habits were very Germanic and, frankly, a bit of a shock for this American. We were all salaried employees. Yet, everything started and stopped on the exact hour; work began at 7:30 on the dot. Work ended at 4:30 and the place was a ghost town at 4:35. No bathroom breaks (except for the rare emergency) or cigarette breaks except during the scheduled break time. Coffee was an interesting story. The morning break was from 9:00 – 9:10. One person would be assigned to make the coffee for the day and would begin at 8:55 and clean up and put the coffee away by 9:15. No other coffee breaks during the day.

The German attitude toward work in that company – work hard not long – was brought home to me one day that I was working late. It was nearly 6:00 pm and my boss, the CFO Herr Haiser, had just arrived back from a business trip and was collecting some items before heading home. The exchange went something like this:

Herr Haiser: “Go home!”

Me: “I can’t. I still have a lot of stuff to get done with the strategic plan…”

Herr Haiser: “Go home!”

Me: “Why?”

Herr Haiser: “There are only two possibilities why you are working late. The first possibility is that you have a tremendous amount of work to get done and you have been working diligently and non-stop all day. In that case, you have put in 10 hours or so of hard work, your mind is fried, and you can no longer be productive. So, go home and re-charge your batteries for tomorrow. The second possibility is that you have not been working hard all day. In effect, you have been procrastinating, screwing off, and are likely just now getting started on your real work. If that is the case, then you are wasting time, wasting space, and being unproductive. So, get out of here. In short, in either case you are useless to the company and me right now, so go home.”

By contrast, there is a real American trait that lauds those who achieve success through long hours. Think of the point of pride of working late, working weekends, or always being available and on call. Think of the start-up ethic of long hours, heavy caffeination, and no sleep that entrepreneurs, investment bankers, lawyers, corporate executives and others wear as badges of honor. Think of your visceral reaction if someone tells you that they are very successful but only work 30 – 40 hours a week (disbelief, perhaps a twinge of jealousy, and a feeling that they are just lucky and have not “earned” their success).

In the end, the most effective and the most successful people work hard – doing the most important tasks first; simplifying, minimizing and eliminating the non-important; batching their work to give undivided, concentrated attention – without working too long.

I suspect that Ms. Sandberg might just be one of those effective and successful people. As such, her 5:30 pm quitting time has publicly punctured the myth of “long work.” Perhaps, we should all learn a lesson from her.

And, by the way: What’s for dinner?