No one complains of having spent an entire day doing 'productive work'. Busywork, on the other hand, is mindnumbing.
It's possible that if you have a job where your tasks (your busy-ness) is programmed by someone else, that being busy is your job.
For everyone else, though, busy might be precisely the opposite of productive.
Maybe the best exhortation isn't to, "get busy."
Instead, perhaps it involves slowing down enough to feel the fear. The fear that we might only hear in the quiet moments, in the gaps between crises.
The fear is a necessary part of actually being productive in doing creative work.