All I can come up with is "I want to be a nurse practitioner so I can take care of poor people" and that would sound pretty lame and pretentious on an admissions essay.
I'm applying for NP school and the essay topic is your typical outline your career goals and why you want to be an NP. I know I want to be an adult health nurse practitioner and take care of economically disadvantaged population(mainly because I've come from a poor immigrant family and know how crappy the healthcare system is for poor people and the issues that they face). I also volunteered at a nurse practitioner run clinic for a couple months where I got to see what NP's do on a daily basis and really think I would enjoy doing it.
But kinda stumped on what to include or write about. The light bulb just won't turn on!