my dear teacher, thank you very much for your help during the time we spent together. You help me a lot and I learn a lot from you. Whenever I have a question, you're so patient listening to me and help me find the answer. I'm grateful to you and I promise that I will try harder and make contributions to our country and become a useful person in the future.
Thank you again and the best wishes to you!
yours xx
大概先说一下谢谢老师的帮助,从老师这里学到了很多东西,受益终生.然后说一下自己会不辜负老师的希望继续努力,争取更大成绩.最后再次表达对老师的感谢以及向老师祝福.
楼主可以根据自己的需要把我上面的文字加以修改.