Let's face it--writers are full of themselves. How else could we assume that people will actually pay to read the products of our thoughts and imagination? It's a pretty big assumption.
So being a bit arrogant is actually part of the muse, but one flaw I see in a lot of beginning writers is that they spend more time talking about being a writer than actually writing. They boast to all their friends about the great novel they're working on, when in fact they haven't made it past page ten after five months of "work". They get into flame wars on newsgroups, arguing about all the tired controversies that crop up continually in such places, when they should be saving that energy for their writing.
My advice--shut up and write!
Yes, this blog counts as talking about writing, but I spend about sixty hours a week writing, researching, editing, or pitching, so I've earned the right to gab a bit. :-)