Most people who keep a diary/ journal write with an audience in mind. They write to someone, even if they don’t ever plan to let anyone else read what they have written.
Try writing a diary entry about your day, or pick an average sort of day to write about. Choose who your audience is. As you write change your audience to someone else about midway through. How does this change what you write and how you are writing it?
Found on Wikipedia :
Escribitionist – a term for a person who keeps a diary or journal via electronic means, and in particular, publishes their entries on the World Wide Web.