Don't say no for them. Whoever the anonymous them is. Don't you dare. Whatever you're making, stories, art, macrame sex toys, whatever creative thing you're doing, don't you dare look at it and decide it's not good enough for the market and then tuck it away in a drawer with a dramatic sigh about how if only you'd had THE ONE MAGICAL ADVANTAGE you could sell it and quit your day job mopping up the exorcism room after those three rogue priests wander off to congratulate themselves on a demon well banished and break into the sacramental wine.
1) Creative people are naturally down on and extremely critical of their own abilities and will underestimate themselves. This is an actual scientific fact*.
2) In my travels around the world I have seen some hideous shit sell, but YOU make cute, fun stuff. Whatever you make. Because the thing you make reflects your taste and style and classy self as an artist.
3) It's a big world. Suppose the publisher/art gallery/etsy store you selected and made your thing specifically for rejects it? They turn up their nose at it? They tell you it's just not right for them, the tone doesn't match, it's too similar to a thing they already have? So what? So what? There's a lot of publishers/art galleries/websites that your thing will be treasured and upvoted and sell. Use your google-fu and find them.
But if they're saying no to your stories or art, it doesn't mean they're wrong. You could be wrong.
1) Are you really ready to shove that project out into the cruel, indifferent world? Has an independent editor flagged all the typos? Have you played with your handmade wooden puzzle enough to know you need a second coat of sealant to keep the paint from flaking? Can you take a decent picture and understand how to edit and upload it? Do you check your email often? Does your 'contact me' button actually work?
There is NOTHING more frustrating than wanting to buy something, but the artist has vanished. Then I'm reduced to twitter stalking and wondering if @battlecat77 is the person who makes that awesome medieval armor for cats, but they never reply. If I can't reach you, I can't buy the thing. So you make no money. That is a badness thing. Do you check your spam folder once a week for hapless customers that use hotmail? (My gmail always bounces hotmail, I never told it to do that, it just does. It also ignores me when I told it to stop. Apparently Google does not obey the second law of robotics.)
Are you ready? Is your work ready? If you aren't confident in your own work, then do your research, see what's out there, and if your stuff is of comparable quality, send it out. Let them say no. Don't you say no to yourself before anyone else even sees it.When the first buyer says no, then find another. There's always another. Another publisher, another shop, another way to sell the thing you made. Get creative, you ARE creative. You MADE a THING. You WROTE a SCRIPT. You can find a way to sell it. I believe in you.
2) Are you doing lots of stuff? The more you do, the better you become. The more stories you write, the more stone walls you build, the more exotic gerbils you raise, the better you become. This is also a fact, scientifically proven by anyone who has practiced any skill whatsoever. Branch out. Expand. Even if a thing has been around thousands of years, you can still put your own unique twist on it.
Books are old news, but remember those 'Choose Your Own Adventure' novels? A novel new twist! I rest my case.
3) Are you for-real serious about this? Are you writing at least five days a week? Do you treat it like a job and sit down, unplug the internet, and stare at a blank cursor until story happens? Do you have an outline, or at least a summery with the beginning, middle, and end of the book to keep you on track? Substitute the word project for book. Do you know how it's going to happen? Etsy, ebay, and craiglists are full to the brim of weekend crafters churning out random stuff and barely making their material cost back.
Profit... is a funny joke, but knowing the outline of the project and the steps you have to take to accomplish the goal is SO IMPORTANT I CAN'T EVEN TELL YOU. BUT I WILL.
4) Did you write your goal down? No? Go and do that. Right now, hop to it! Find some paper and write down what you want out of this thing you do. To be published? To make X amount every month? To spend your life traveling from one craft fair to another like some sort of modern hippy in an SUV instead of old VW van? To develop a variety of guinea pig with hair so long you can cackle like Dr. Frankenstein and shriek 'IT'S ALIVE', because you've just created a tribble?
Write your goal down, pin it up somewhere you see it EVERY DAY, and do something every SINGLE day to accomplish your goal. Even if you just have the time/mental bandwidth to do one thing to reach the goal, one thing a day will get you there. Do nothing a day and you'll never get there.
I leave you with this for further reading.
Go get'um tiger.
* Based on a random survey of creative people I know and didn't actually bother to survey.