Consider these two scenarios:
In one scenario, you spend the majority of an 80-hour work week sending e-mails, accepting every meeting invite that comes your way, and sitting on said meetings.
Is this exhausting and hard work?
But was this best way to advance your most important projects? In some cases, perhaps. In many cases though, it’s unlikely that endless e-mailing and back-to-back meetings were just the thing your projects needed.
Now consider another scenario where you spend a 40-hour work week limiting yourself to e-mailing for 1-hour a day, selectively rejecting meetings that are not mission-critical, and blocking out time to think & address your highest priority projects.
Just like the first scenario, this is hard work too. Only in this case, the idea that your most important work will have progressed during this week becomes much more plausible.
Hard work is important, but more important is understanding where it makes sense to work hard.
Without thinking carefully first about where to put your energy, you risk doing a lot of things without getting a whole lot done.