The best way to see if your writing is working for anyone other than yourself (which is the point of most writing, right?) is to get another reader or two. Someone who won't just be unwaveringly supportive, but will point out what is good and not so good about what you've already got. It's not always easy to find such a person, who both "gets" it and can point out its relative strengths and weaknesses. Remember that everyone's take is subjective, and think about the suggestions you get before acting on them.

For concepts that didn't quite come out on the page the way you hoped, try talking them out with someone else, casually. Maybe the right turn of phrase will come up that way.

Most useful I think is to get some space between the creation and the revision. Most of the time after I've "finished" writing something I can almost immediately see ways it could be better or places that don't seem to work. I try to resist the urge to meddle right away, filing away that thought for later. If I come back to it and have the same reaction, then it's probably something to work on. On the other hand, maybe you'll look at it and say, "Hmmm, maybe it's not so bad after all." Some things are better left a little raw than utterly polished.

If it's a question of submission anxiety, there's no replacement for just doing it. Find contests with submission deadlines to enter. They're usually good because they a) force you to let go of your "baby", b) make you leave the story alone for the period during which it's being reviewed, and c) tend to have a set timeline for announcing results, so you're not left hanging indefinitely.

--ich sage nicht, was ich will, sondern was die Sprache will--