I came across this a while back. It is for a residency application but I think lot of it applies to fellowship application as well.
"The personal statement should not be a biography. Rather, it should consist of three basic parts. First, the statement should explain what it is about the specialty you have chosen that most appeals to you. Secondly, it should present carefully selected information from your background which provides evidence that you have acquired the skills, traits and abilities which program directors in that specialty desire in their residents. The third section should communicate any particular aspects you are looking for in a residency program, a brief description of your long term goals (such as the type of practice or practice setting you hope for), a summation line which lists the strengths you would bring to that program if accepted, and finally, a thank you for their consideration of your credentials."
GL.