"why, I doubt I can ever be so good ... why can't I write good stories, especially when I'm so much criticized ?"
...
"How do I build up a normal, healthy self-confidence ?"
I wonder whether it is possible to build up, to develop any - what would you say about that ?
You like writing, and from what little I have read from you so far I think you are talented. That's as good a basis as there can be.
I agree with Winterfox: Every writer gets criticized. You can learn from it by trying to integrate what you think is right and ignoring what you think may be right for others but not for you.
I don't know the proverb in English: Es ist noch kein Meister vom Himmel gefallen... (Means: You have to practise to become perfect).
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.
As to self-confidence: When I was younger, I wasn't even able to look up when walking a street. (Somebody might notice me...) And if somebody looked at me I blushed. Inevitably. It was hell. In school, I always got very good marks for my written tests, and the worst possible for my oral contribution. Even if I knew something, I just could not speak in front of all those people (my classmates, the teacher,...). <img src="/ubbthreads/images/graemlins/puppyeyes.gif" alt="" /> I thought I was stupid, ugly, different.
I will never be someone who likes to speak in public, and I still blush sometimes. But I can say what I want to say in front of others, and if I blush I don't give a ... I can't tell you how I developed some self-confidence, sometimes I think I was just fed up with being shy. This won't help you much, I know that, but you asked if it was possible to develop self-confidence.
My answer: Yes, it is possible. Just don't give up. <img src="/ubbthreads/images/graemlins/up.gif" alt="" />