One possible version:
Dear Daniel,
I am writing to tell you about my problem with my parents. I don’t know how to deal with it and would like your help.
You know I am interested in life on practicing colour therapy. I often advise my classmates on how to use colours to change their moods. In my spare time I often go to the library to find something to read. Sometimes I even stay up late watching the documentaries about it. This makes my parents very angry. To them, good marks are everything and they think I should spend more time on my lessons.
I think healthy hobbies can help me with my studies. It will also be good for my future development. What’s more, hobbies can help me relax and make my life more interesting. But I don’t think my parents understand me. I feel bad about that.
What shall I do? Can you offer me some suggestions? I am looking forward to your early reply.
Best wishes
Yours,
Lin Hua