For me, writer's block is fear.
It's the fear that whatever comes out when I'm plunking away at the keys will be total crap.
It's easy to show people your writing when it's pretty good. It's a lot harder to show them something that's clearly not your best. And that's when the fear comes in.
This is despite the fact that sometimes my best breakthroughs when I write crap and then show it to my writerly friends. Many times they can put their finger on what sucks about something I write and how to fix it. And when that happens, that's when my writing really improves.
But sometimes I can't overcome my fear and just get stuff down.
This is my challenge this week.