What is a personal trait of The Diary of Samuel Pepys?
Samuel Pepy's The Diary is, of course, a diary, so there are numerous personal elements in it. "Personal trait" is a bit vague (physical characteristic? writing style? what he experiences?), so I'm not sure exactly what you're looking for, but I'll do what i can.
I guess I will mention one personality trait. The author is reflective. In his entry for Sept. 14, 1615, he writes:
When I come home I spent some thoughts upon the occurrences of this day, giving matter for as much content on one hand and melancholy on another, as any day in all my life....
Of course, reflecting must surely be a natural act for a diarist, but it is as well a personality trait of Samuel Pepys.