Any skill improves when you practise it, and we've all discovered that in non-writing ways. Writing is exactly like knitting, painting, ju-jitsu, public speaking, riding horses, driving cars, mathematics, running marathons, learning computer code, becoming a doctor (they call it 'practising medicine' for a reason!).
If you're like me, you probably made wonky things in woodwork and crochet before getting the knack. And the knack was just making enough time to practise skills, perhaps with a little guidance, before making a cupboard, or a scarf.
We even learned to read through practise: we begin with Dr Seuss, not James Joyce (and let's face it, even now not all of us are ready yet for Ulysses).
As for writing: the written word is an invented (rather than evolved) method of communication. It's much, much, much younger than the spoken word and is, in human evolutionary terms, a recent and effectively artificial skill.
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In fact, I suspect that because most of us learn to read and write at school, we take it for granted that everyone reads and writes well. But not everyone takes the time to develop strong writing skills.
So if you think your writing isn't going well, don't be discouraged! Write often, write again, write some more. Keep reading, too, to expand your vocabulary and absorb ideas on sentence construction, story themes, and how to reveal character, motivation and plot. Consider writing courses on aspects that give you trouble so you can find different approaches to explore. Then write, write, write some more.
And don't forget that writing has a built-in do-over called editing. We no longer set our writing in stone. If you're not happy with the first draft, play with those sentences, hone those skills! Honestly, it's incredible, the good fortune we have to improve our competence in this strange skill of putting squiggles on a surface. We get to practise the order in which those squiggles go for the best effect, and we get to change and change and change that order without losing the essence of how we began.
Everyone published now began the same way – with a set of tools (the alphabet) and a drive to arrange those squiggles into a wonderful order, to convey a story from their heart and brain to your heart and brain.
And none of them began perfect, and all of them got better with time, through experience, which is another word for constant practise, listening to and incorporating feedback on how to improve, and then practising some more.
Now – write!