I don't know the proverb in English: Es ist noch kein Meister vom Himmel gefallen... (Means: You have to practise to become perfect).
The English version's exact wording is "practice makes perfect." If you want to know. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
So: keep on writing! Have you considered attending courses? I have no experience with writing courses, but with other courses. Apart from the contents I often find them very encouraging.
I think you can self-teach and learn on your own -- that's what I've done, anyway, and I don't feel like I've missed anything. These courses can sometimes be less than beneficial. A few acquaintances of mine who have attended writing courses have told horror stories about peer-editing where you
have to say only positive things about the other students' writing. Which is, IMO, rather childish and in the long run, detrimental. (One of the people I know had to lie through her teeth about the short story of a classmate. She found it offensive, badly written, and all around awful. What she ended up actually saying was "This is interesting and has potential." What she didn't divulge was the fact that she also found potential in chimpanzees banging their heads randomly against the keyboard.) Of course, I'm sure that good writing classes exist, but I haven't run into any... yet.
Incidentally, I'll add this: no one is beyond, or above, criticism. No one. Not even authors who occupy first slots of any bestseller lists. Not even critically acclaimed authors who have won Nobel/Pulitzer/Booker Prize. I had some fun seeing
Romeo and Juliet torn apart, as well as reading complaints about Terry Goodkind, David Eddings, Jean M. Aules, Laurell K. Hamilton, and Robert Jordan -- to name but a few.