I don't know why people write in blogs.
To be completely honest, I've always considered myself a good writer until I came to Berkeley. I think it's because I see writing as an ultimate check for self-confidence; I only write well when I'm confident I can be good at it. Doubt destroys all possibility of writing something good - I double check I re-write, I ask others what they think and by the time I'm done it's lifeless plastic.
But maybe that's not why I haven't written in so many years.
