I think writing practice* is the most important thing you can do for your writing life. Of course you need to work on your stories or articles, but you need to give attention to writing for the sake of writing, too. Just as an athlete or musician or dancer must practice regularly to keep themselves in top form and do their absolute best when it's time to perform, a writer must practice their craft so when they sit down to the page they can tell the story that is in their hearts.
So what exactly do you get from regular writing practice? All of this and then some:
Sharpen your writing skills
Writing practice, even the most free form, stream-of-consciousness style, gives you a chance to play with words and sentences, practice descriptions, toy with dialogue. It lets you build better writing skills without the pressure of trying to become a better writer while also trying to write a story.
Learn to write on demand
Sitting down to write regularly, especially if you set a goal to write for a certain amount of time or number of words or pages each session, trains you to start writing when you sit down at the page. Sitting down with your notebook or at the keyboard becomes all the trigger you need to let the words start flowing.
Discover your true thoughts
Writing practice lets you examine your own thoughts and opinions on whatever subject you choose to write about. There is no influence from others besides what you bring with you to the table from your own experiences, reading, etc. There is no need to worry about what readers will think about what you have to say because writing practice is your own personal writing and not meant for readers. Writing practice gives you a chance to dive deep into topics and then use what you've written as a springboard for further exploration so you can get down deep into your own thoughts.
Quiet your mind
Writing practice is meditation. It lets you clear your mind, quiet your thoughts, focus on just your hand and the pen and the page (or the keyboard and screen). The more you practice, the more you will find that a good, solid, regular writing practice is just as beneficial to your state of mind as sitting in meditation or practicing yoga.
Build a body of work
In writing practice, you write. You write a lot (you'll be surprised how many words pour out even in a 10 minute session). Most of it will not be useful--it will be a lot about worrying about money and your health and your dog and your job. It will be a lot about the world around you. But it will also be true thoughts from deep inside you, snippets of dialogue, descriptions of what's outside your window. And all of these are things that can be used for further writing practice and also in stories and poems. The more you write for writing practice, the more you have to draw on for later projects.
Banish writer's block
When you get in the habit of writing anything that comes to mind when you sit down in your writing spot, the habit starts breaking down any writer's block you may experience. When you become used to keeping your hand or fingers moving, keeping the words pouring out no matter what else is going on, this carries over to your other writing. If you become accustomed to starting to write as soon as you show up at the page, you will also start to write immediately when you show up for your story. Giving yourself permission to write fast with no worries for content loosens you up to write whenever you need to.
I hope I've convinced you to start a regular writing practice aside from your stories, poetry, and so on. It's really worth your time. Give it a shot. Try it out for a couple of weeks or, even better, a whole month. Then stop back here and let me know how it's going.
*Writing practice is writing for its own sake. It is letting your thoughts spill onto the page free form either by writing whatever comes into your head or by using prompts to get you started. It can also be targeted writing practice where you do exercises to build your description skills, dialogue skills, etc.