work out.
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My personal record for '"isn't working out" is when my Haiku Muse dropped this on me:

"Four-space Tapestries"

And has not given me any help at all for the 12 (lousy) syllables needed to finish the haiku.

And that was nearly >forty years< ago... and She is not answering her "Supplication phone" ...
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Here's the thing (OK, one of the things):

The way to have good ideas, is to have >a lot< of ideas. Grab them from anywhere. Oh, and keep a notebook - ideas, good and bad, can be just as fleeting and evanescent as dreams (are supposed to be.)

Dreams,

Supermarket checkout (till?) lanes tabloids,

Many authors (including here), 'give away' their excess ideas,

Extend a story, or sequel it. Come to think of it, I have tickling my mind, a story set in Ray Drouillard's "fae and were" universe, that he set the M.Y.T.H. universe ...

https://en.wikipedia.org/wiki/Brainstorming. A good session might yield a winner, 2-4 maybe's and a thousand+ post-its into the recycle bin. Brainstorming, like many other activities, is better with friends ... but we can do it alone. Come back the next day and bang your imagination against the whole list,

Go for a walk or a drive, preferably in nature. Some forest preserves near me are set up so the road winds thru the preserve, from parking area to parking area. So I can drive, park and be less than 10 meters from the nearest tree,

'Bang' two or more stories together,

Take any news item (or 'Wired' or Scientific American article - OK, I'm a geek) - and 'run away with it' - build a world where the news item is 'every where' (flying cars (uhm, they now exist), cars that run on local streets, but 'latch onto' a moving roadway for long-distance/highway travel (oops - Heinlein, "The Roads Must Roll"), 3D printers that can 'print' a restaurant-quality meal - in the works, ...

Build a Utopian future - Eolwaen is good at this.

Tell a story, and at the end, wreck our expectations and stereotypes (many of us have taken such a "Bru-ising" ...)

Look at things sideways, or reversed (all the time at BCTS), or upside down ... "Stand up" and "Improvisational" comedians are good at this. Steal the idea, file off the serial numbers and run with it.

Oh wait -what an act that would be - a comedian/escape artist telling jokes while hanging upside down and getting out of a straight jacket....

See how it works - I banged 'look at it up-side down' against stand (right side up) comedian ... Oh!

Heck, get one of those 'flip chart' pads and hang it on the fridge or by your computer: Here's one of too many: https://www.officedepot.com/a/products/8024487/Office-Depot-... ... and a 'dozen pack' of colored pencils
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Oh, and maybe your 400 word story - is really meant to be only 400-500 words. Maybe the last line will be "What is our World gonna look like twenty years after (story) happens?"