A karate sensei I know often says "it's not practice that makes perfect, it's perfect practice that makes perfect!"  The point is, if you don't practice what you do properly, then you won't end up doing whatever it is you do properly.  That's certainly applicable to martial arts, but when it comes to something like writing a blog, I'd suggest otherwise.

If you want to be effective at writing blog posts, you do need to practice.  However, a blog is really intended to be your voice - your opinion is what matters and will drive people to read your posts.  Too often, I read blogs that are monotonous and boring.  They are written as if read from a script, much the same way when a speaker reads from a teleprompter.  It just doesn't sound genuine.

So I submit that when it comes to writing a blog - practice can make perfect...just don't be too perfect and you'll find many more people will listen to what you have to say.