Write what you know. Your life is a great place to start. You have something you are doing that no one else knows about, like a job or location or life challenge. Start there.
Write what you know. Be sure to talk to lots of people so you know more.
Write what you know. So write about monsters you invent, because who’s going to argue?
Monsters shouldn’t glitter unless they kill people with glitter.
Write things that would embarass your mother. This may not work if your mom likes the Kardashians. If your mother has no shame, try for “dismay” or “repulse”.
The best subtext is unintentional. That is, if you write to convey a message, that message will consume everything — characters, plot, and eventually your ability to interest others. Those you wish to persuade will dismiss you for preaching and those who agree with you will think you’re a dilletente and ignore you. Write your story. If you realize, hey, this story is awkward and makes me look nuts, then work with that. Embrace it. There is a market filled with people who are also awkward and nuts.
Remove as much as possible from your story, especially if you’ve seen it before in other stories. That goes double if you are writing a pastiche or a monster that’s been done.
Writing is not theraputic. Speaking with a cleric, health professional, or mature friend is theraputic. Writing can improve you the writer if you write with the idea that you the writer are wrong and have been for many years. That is “cathartic”. You may have a really good story when you’re done, too.
If you wish to inspire with your writing, make sure your conflicts and antogonist are treated with respect.
Everyone disagrees. Even twins disagree. In theory, clones raised in identical circumstances would disagree. Your character has to do impress you and also make you facepalm.
Even locations have character arcs. Game of Thrones wouldn’t have worked in a thriving, newly born empire. If Salem’s Lot had been a vitalized town filling with immigrants or yuppies, Barlow would have been burned before his antique store opened.