Dear Mr.Green,
Thank you very much for you letter and I am sorry to hear that you have trouble sleeping well these days.
I would like to present you with three suggestions.First,please do not think about your work when you are at home resting.Second,you might as well do some light exercises to tire your body up.Thirdly,listen to some music.Music is magic and you will feel that after a while.
Please do keep me updated of your progress and don't hesitate to let me know if you need further advice.
Wish you a good night's sleep.
Yours Sincerely,
Dr.Smith