Dear Mr/Mrs XXX,
How are you now?
I have been missing you since I graduated from the senior school. I'm studying in XXX university now. My college life is wonderful and I like my major.You give me a lot of help when I was in senior school and I feel so lucky for having ever being your student.I never tell you before,but in my heart, you are my best teacher and a good friend forever.I still remember your jokes and your kind smile.You always encourage us to learn more and never give up.Sometimes you get angery because we always make the same mistakes. You can't help saying some humiliating words when we make some stupid mistakes.I hate you for that before, but now I know love well, whip well.(爱之深，恨之切）You love us all, you love everyone.You never tell, but we know you hope all of us will be successful and we will never disapponit you.
There are some questions occur in my mind when I think about you. How's everything going now? Are you in good health?Are you still busy from dawn to dust? Are there some naughty boys in your class? Are you happy everyday?
I know you must be busy, but I still hope you can write me back soon and tell me your life.I'm looking forward to receiving your letter.
Sincerely,
XXXX
写的比较中性了，你往里面再添点就行了。不同的老师经历啊，性格的都不一样，你的经历也不同，所以你自己再修整下啦。
