I encourage all you young writers out there to keep plugging away at it. Don't get disheartened.
For every success I post here, I have multiple rejections.
If you are a writer, you WILL be rejected. Develop a thick skin. Learn from constructive criticism and ignore the rest. Especially ignore the little devil on your shoulder who tells you to give up because you're no good.
Finally, do your research before submitting your work. Make sure you're sending it to the magazines, agents, and publishers most appropriate for your style and subject matter. Be methodical in your submission process and keep track of everything.