Advice for younger writers

When you write something and give it to someone else to evaluate, if you are told it is not good enough, write something better.
It is easy to take criticism as a fault of the reader, that they don't 'get' your work. You can end up in a viscious cycle of giving out your work, getting bad reviews, blaming the reviewer, sending out the same work, getting bad reviews, blame the reviewer.
Stop it.
Learn from what you have created and move on; re-read your work. If you can't do any better then chances are, you are really not that good.
If you write more and receive more criticism, keep writing. One day you will have two things: a mass of work, and a plotted history of how you got where you are today. This is very important because it proves that you never gave up, and probably that work number 1 is not as good as work number 1000. You will see your progression and your improvement. This is your life lesson and it is something you taught yourself... if you still are a struggling unknown, consider the lesson you have given yourself your prize. Consider also that you really are a writer.
If you gave up at number 1, you are not a writer and were certainly not good enough.
Success is the point at which you creat something that speaks to someone else, even if that is just one person. Feel happy with what you have made, because no-one in the world could have done it but you. Never judge your own success in terms of who 'makes it', their work is no better than yours, it just landed on the right desk... a desk owned by someone with no real idea of what is good or bad, just what can sell.
If you only write to sell, you are not a writer, you are a salesman. This is fine as long as you are honest with yourself about your true intentions.
Now write something good.