To assess your actions as adding to this legend or not seems a pretty good indicator of whether you should be doing them.
Seth wrote about the stories of products and services, the amount you pay for one over another is the story - it's the value we attach to it.
As individuals we are telling our own stories, building our own legends. They are what makes us special, what makes us unique, our individual worth over someone else. They occur sometimes in private, others in public, and often these domains cross.
I think that's what blogs are - or should be - a public manifestation of our stories. We may not wish to share it all, publish every chapter, but we need to be happy it represents "us" and adds to our legend.
We can become distracted, post things for impact, attention, notoriety, but these do not add to our legend - they are not parts of our true story.
We need to discover that and this in turn will inform our writing.