One possible version：
Dear Tom,
How is everything going?
These days I worked as a volunteer of Shanghai World Exposition 2010. It’s a valuable experience for me. In order to provide better service for the World Exposition, I made every effort to practice my spoken English, and have made great progress. Second, as a volunteer, I worked very hard and felt the happiness that went with my voluntary work. What’s more, I learnt more about cooperation and responsibility, which will benefit me a lot in the future.
I’m proud of becoming a World Expo volunteer. It’s an opportunity of my lifetime and I will cherish this beautiful memory forever.
Why not become a volunteer yourself?
Looking forward to your reply. Take care.
Yours,
Lihua
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