Although the actual process of writing can bring us a great deal of pleasure, the purpose of writing is to be read. And to write well, you do need to think of your reader.
If you are writing for a certain age group, visualize a person of that age reading your work. Or if writing a factual piece, think of what the reader wants to know and how you can best put the information across. Similarly if writing a tense drama, imagine the effect of your words and scene on a specific reader.
By writing with a reader in mind, your writing will not only be more appropriate but so too will your style and vocabulary.
Don’t forget, if you have any writing questions, do please email.