Successful writers remember that people will read a book one person at a time. Some say they write for themselves, others have a real or imagined individual in mind as their reader.
By imagining one person as your reader you avoid a danger: trying to write to please everyone.
To paraphrase Abraham Lincoln, you can please some of the readers all of the time, and all of the readers some of the time, but you cannot please all of the readers all of the time.
If you doubt it, read people's comments about the most popular books on Amazon; there are those who hate even the great classics.
Trying to please everybody will make you censor anything that might offend anybody--which won't leave you with anything but the blandest prose imaginable. It can also be the cause of writer's block.
Who to choose as your imagined reader? If you're happy writing for yourself, that's an easy choice. Otherwise pick someone, real or imagined, who:
* enjoys the genre in which you write
* is intelligent (never underestimate the intelligence of your audience)
* is friendly but not uncritical (in other words, they'll notice mistakes)
* is someone whose company you enjoy (or would if they were real)
* is eager to read your book
Having this kind of individual in mind makes the writing process more enjoyable and keeps you on track.
(Do you want a writing coach but are not prepared to spend the kind of money that requires? The next best thing is my book: "Your Writing Coach," published by Nicholas Brealey and available from Amazon or your other favorite book seller.)