I can’t say I’ve gotten very much from writing teachers, but one of them in college used to say, "writers write." I didn’t get it at the time, until I began to meet people who wanted to 'be' a writer, but never wrote anything. I learned the difference between being and doing, and that you don’t do what you are, you are what you do.
There is nothing wrong with writing 'for the drawer,' as people used to say. Many writers keep journals that may contain bits and pieces they will use, but the journals themselves are for their eyes only. Today, the internet gives us another way to go. Making your writing available to an audience, even if it doesn’t find one, is slightly different than writing for yourself. You are, at least, bringing the idea of readers into the equation.
Even today it is rarely a good idea to publish a first draft. Ideas are the same way. A writer I used to work with called it "first land visited." I’ve known too many people whose first idea is always their best because they give up so easily.