Why was its hard to belevie to aurthor that her grandmother was once young and preety

Looking at his grandmother who short, fat and slightly stooped in stature, it was very difficult for him to believe the stories of his grandmother's beauty in her younger days.?The author had only seen and known his grandmother as an old woman. It had been the same situation for twenty years. As a child, therefore, he found it hard to believe that she was young and pretty once upon a time.