Handwriting is a graph of your personality and your way of thinking. With time there are changes in your personality. So the change also reflects in your Handwriting.
Many people say that their Handwriting deteriorated with time. What they generally mean us that the legibility or presentabilty of the writing reduced. A legible Handwriting means clarity of thoughts. And an illegible writing means some unexplainable way of thinking. So people who complain of worsening of writing have chosen to be Manipulative in some area of life to cope with the situation.
Health is seen in the Handwriting strokes. Illegible Handwriting can cause stress and lifestyle related health disorders like diabetes.