There's a difference between trying your damndest during working hours, and hustle nonsense. In my experience, employers see time spent on site as a measure of success more than how productive you are during your regular workday.

So I read that to mean, don't kill yourself working unpaid overtime. You can still do a great job, working established working hours. I agree with that 100%. While I'm at work, I'm at work. But the moment that the day is over, work does not exist and will not exist.