[...] and be excellent at prioritizing competing demands.Let's be clear: anyone can prioritize competing demands. The trick comes in performing a prioritization that can be approved by someone ultimately responsible for your work.
The textbook example (that has never happened to me personally): an important, customer-facing server is in flames. And the CEO's secratary can't print some powerpoint slide handout for a meeting he's about to go into.
What's more important?
The fact of the matter is that to the company, the server is more important, but most of the time you'll get into trouble if you don't make sure the CEO gets his handout.