"In writing, your audience is one single reader."--John Steinbeck. That reader, in my case, was me. Or is me. Sometimes, it is a friend, a couple of close friends or loved ones.
But in the last few years, I have, occasionally, lost my way. Because, the need for survival and money tends to distract writers from their original purity.
If a piece of writing has been cathartic for me, or if I have enjoyed rereading it, sometimes years later, and often with the same or greater pleasure than when I read it the first time--then my original purpose has been served.