The advice to write every single day has been given to most people thinking about trying to make something of their ability to write. It is simply the best advice for FIVE very good reasons.

Get Writing Fit
Most people don’t really spend much time writing in their daily lives. A book can be anything from 20 000 words for a short non-fiction, to around 80 000 for an average novel to a couple of hundred thousand for really in-depth non-fiction and speculative fiction. So, to write a novel, you need to write 1000 words for 80 days. And that’s just the first draft. That’s assuming everything you write is on target and useable. Call 3 months for the sake of symmetry. That’s a lot of work. You need to be writing fit to be able to do that.

Get Better
Writing is just like everything else: the more you do it, the better you get. If you write something every day, you will write an awful lot of rubbish. At first. But you will see that, over time, the rubbish you write on your worst day is better than the medium stuff you wrote on your best day 6 months ago. Just like playing golf, cooking or anything else in life. Repetition really does improve your skills.

notebook for a writer
Write every day… by hand if you have to!

Live Inside Your Idea
It’s really easy to think you’ve got the best idea ever for a book when you only ever write anything once every couple of weeks. When you dive into that well every single day, you start to see the gaps and the holes in the logic or thinking. You begin to realise what else is necessary. This can be de-motivating. But seeing the pitfalls is the first step to fixing or avoiding them. You’ll hit them sooner or later anyway, so might as well dive in and find them fast.

Try Different Kinds Of Writing
The rule says write every day, not write in your own book project every day. On those days when you just can’t you might try journalising, poetry, an article, hell, a list of how much this writing everyday things sucks. That’s good. You are widening your skills set. If you just can’t face your manuscript one day, try writing a whole new set of lyrics to your favourite pop song. Or pen a satirical version of a Shakespeare sonnet. Just make sure you write that day. Something. Write something. Nothing is ever wasted, especially with writing.

Write More Than You Need
No editor or author ever said, “Oh bother! I have too many words, what am I going to do?” But many, many writers and editors realise a little bit too late in the day that there is simply not enough narrative, not enough writing to round off and complete a work. Deviations, additions, bad writing or simple over-writing can all be easily removed and disposed of. As seen above, it’s good practice and makes you a better writer. Rather be there than sitting with too little text and deep uncertainty about how to join the dots of your story.

Stephen King has excellent advice on this subject in his book, ‘On Writing.’ (I paraphrase here liberally)
1. Choose a place where you can write every day without being disturbed.
2. Make sure the place itself does not have lots of distractions
3. Pick a time of day when you can commit a set period of time every day without being disturbed.
4. Start with ten minutes for the first week, work your way up in ten minute increments until you’re putting in an hour every day.
5. Spend all the time you are in that chair in that place during that time WRITING
6. Do not use that place or chair or time for anything else except writing.

You will see that after 2 weeks the power of the force of habit means you will just start writing the moment your rear end hits the designated spot at the designated time. It’s wondrous and oh so simple.
Try it.