Dear Tom，

I'm happy to have received your letter． Now I'm writing to express my thanks for your care and tell you something about my study and life．【写信目的】

Since entering Senior Three， a great change has taken place to me． First of all， I'm studying much harder than ever with the purpose of preparing myself for the College Entrance Examination． Besides， so many tests do we face every day that I feel extremely stressful， even lose sleep sometimes at night． （高分句型一）Occupied with my study， I can't afford any time to take up my hobbies， let alone， playing computer games as before．【陈述情况】

However， I have decided that I will try to adjust myself to Senior Three． While studying， I will make wise use of my time．（高分句型二） By keeping a balance between study and rest， the learning efficidency， I believe， can be improved and my dream will come true．【应对措施】

Best wishes!

高分句型一：Besides， so many tests do we face every day that I feel extremely stressful， even lose sleep sometimes at night．

另外，我们每天都要面对这么多的测试，我感到压力很大，有时晚上甚至失眠。

本句中so many置于句首，句子用了部分倒装。

高分句型二：While studying， I will make wise use of my time．

学习的时候，我会好好利用我的时间。

I与study之间是主谓关系，本句中是现在分词作时间状语。