Dear Mary，
I would like to take this opportunity to express my heartfelt gratitude to you for your help when I was in difficulty。 You have been very kind and helpful since we knew each other。
Last week， I caught a bad cold and had to stay at home for a week。 When I was worrying about the lessons， you came to my home after school and helped me with every subject。 With your help， I didn’t fall behind others。
Again， thanks so much for your enthusiastic help。 Even though you are to about to go abroad for further education I know that I will always stay in touch with you。 I wish you every success in the future and I hope we can exchange more viewpoints on study。
Please keep in touch， and drop in and visit us whenever you are in this part of the world。
Very sincerely
Peter