Dear Mr.John,
I have won the first price at the Innovation English Competition, I'm writing to thank you for the help you have given me.
It was you, who encouraged me when I was nervous and upset. You gave up your holidays, just because you want to help me getting well prepared for the competition. I'm planning to be an English teacher when I graduate, use what you have taught to help others.
Thanks again for your help.
Yours,
Li Hua