Lawyers tend to disagree on the answer to this question.  My personal view is a strong and emphatic ‘NO’.

If you keep a diary, there is a strong likelihood that you will have to give a copy of it to the insurance company’s lawyer.  You can then be cross-examined about its contents.  You could be asked a multitude of specific questions like:  ”You say you have pain everyday, yet there is no entry in your diary that you had pain on December 17, 2007.”

It is far more advantageous if you are the only source of information as to how you were feeling. Besides, recording how you are feeling every day in a diary is annoying to keep up with, and generally unhelpful in maintaining sanity. 

Whenever you see your doctor, be sure to tell him or her how you are feeling and give as much detail as possible. You doctor will record what you tell them in their notes.  This will be helpful to your case when the doctor’s notes are produced in the personal injury claim.