All valid points. Perhaps I'll start a topic elsewhere on the forum to flesh this discussion out a bit. Particularly:
I also think new writers, myself included, have a hard time gauging the merits of their own work.
I think an artist does have an inherent knowledge that something he/she produces is good or bad or great, etc. Sometimes one's ego (whether fragile or overinflated) can skew that perception, certainly.
I'm prepared to work hard and (much more difficult) exert much patience through this process. Once that first publication credit is carved in print, it will get a little easier, and so on all the way to fortune and fame.
It's tough to think that you can wait two months or more on a really solid story, only to have it rejected because it didn't fit with that issue. What about the following issue? Nope. Okay, off to another market for two more months. Frustrating. But that's where faith in yourself and your talents comes into play. Keep reading. Keep writing. Keep getting better and broadening your scope.
I try hard to be objective. Impossible to be completely so, but I'm getting good at it. In the field of horror in particular, I find that SO LITTLE even approaches scary, or creepy, or unsettling...all the things that make horror horror. And I wonder if my tastes are TOO unsettling. Vicious cycle of self-doubt.
But onward to that first acceptance!! Thanks all for the great comments. I think it's good food for thought.