I think sometimes wisdom given to authors about Never Giving Up starts to sound like a broken record. There’s more to your publishing quest than believing in your dream and being persistent, though those are for sure VERY IMPORTANT THINGS. If sending the same piece of work out over and over again is not yielding any acceptances or encouragement, you might as well be beating your head against a wall expecting something to happen when maybe the work itself just isn’t publishable right now.
It can be hard to hear that, and even harder to get someone to tell you so–either people in your life who have read it don’t have a realistic understanding of what’s publishable or they’re not willing to discourage you, and professionals in the industry are usually so busy that they will just reject and move on to something with more potential rather than tell you what’s wrong or what you need to work on.
So if something you wrote just isn’t finding a home, you may need to either get some real writing instruction/feedback guidance on it or just keep practicing, getting better with each work you produce. Maybe at some point you’ll be able to tell what was going wrong with your old stuff. And there really are some instances where you’re not lucky enough to get it to the right person at the right time or publishing just isn’t ready for/interested in what you’re writing right now–it IS always possible that it isn’t your work’s fault. Just don’t let that possibility stop you from finding ways to improve your piece or your writing in general, and please, please don’t accept that the only quality you need is persistence. That doesn’t work in dating either, and sometimes the answer is to work on yourself.