Advice to writers often consists of ‘write what you know’ and ‘writer from the heart’. As both these things are inconsistent – that is, they change constantly – how difficult is it to be consistent in our writing?

Writing a novel can take anywhere from a few weeks to years. It is inconceivable to think a writer’s personality remains static for this length of time. Writers like to learn, change, and challenge who they are and what they think. Thus, at the beginning of a novel someone might write ‘what they know’ at that time. Twelve months later they might ‘know’ something different. If they are still working on the same piece, how do they ensure consistency in their work?
This is one of the skills needed to be a writer. The ability to ‘trick’ yourself into being who you were, in order to return to the time and place of your work. You may bring new words or experiences with you (after all, a work in progress often evolves) but the voice needs to remain the same.
I could work on a my novel today, and would need to find the voice I’ve been using since I started this piece a year ago. The narration, the voice, of the work needs to be steady so a reader can follow the story and not feel like they are being tossed around.
If I also wrote a poem today, I could use whatever voice I thought appropriate to that piece. This could be today’s me, yesterday’s me, or four year’s old me. Whichever voice I chose, I would then need to re-access that voice every time I edited that poem in future, to remain consistent.
Does all this sound confusing? It certainly can be. This process – finding, using, and re-using a particular version of yourself, your voice – is one tiny element of a great big whole that goes into writing, and is reflected in how writers relate to the world. There is so much going on in a writer’s head that they may come across as absent-minded, distant, self-absorbed, introverted, air-headed, distracted, forgetful, a little bit crazy, and a whole lot of weird.
All true. But that’s not all there is to a writer, who is just a person, like you.