Here is my unsolicited writing advice of the day: Read other unpublished stories.
Join a critique group. Find a local writer's workshop. Exchange emails with a few writer friends. However you do it, find some other writer of similar skill level/experience and read their work.
Not only will it help you feel instantly better about yourself to see other people's rough, unfinished mind-babies (instead of the hyper-polished and gleaming books on bookstore shelves), but finding and fixing the problems in other people's manuscripts teaches you valuable lessons about your own writing.
A second piece of unsolicited writing advice: Be careful about accepting criticism.
You'll receive a lot of feedback from your new writer's group. Some of it will be terrible. Critiquing is a skill that takes some time to master. Sometimes people won't "get" your project even if it's not that strange. Some people will make comments that make you wonder if they were even reading the same book. That's all OK.
You don't have to incorporate every single criticism that you receive. In fact, it's probably best if you don't, because advice usually contradicts itself. But when someone points out a flaw and your knee-jerk reaction (be honest with yourself) is, "I know...." then you need to address that. And if every single person who reads the book -- or at least a decent-sized majority of people -- point to a single problem as being wrong with the book, you probably should deal with that problem too.
That's all my advice for the day.