Read a a great post from Brad Feld this morning in which he shared a memo one of his portfolio CEOs sent to his team called "The Difference between Panic and Urgency". It should be required reading for every startup employee (and has just become so for the entire Mashery team).
The post contrasts panic - "a sudden overwhelming fear, with or without cause, that produces hysterical or irrational behavior, and that often spreads quickly through a group of persons" - with urgency - "relentlessness, steadiness and the purposeful pursuit of a goal while “continuously purging irrelevant activities to provide time for the important and to prevent burn-out.”
In every startup I've worked at, people who panicked would fail out fairly quickly, and those without a sense of urgency (and the ability to purge irrelevant activities is key to this) would fail out more slowly. There is too much to do, and too many distractions from things we "could" or even "should" do but are not urgent enough to move to the top of the list.
But bring urgency to everything you do.