Couple things.
1) Your goal is to get admitted to the school
2) Your goal is to eventually get a good job
The essay is for the school to evaluate whether you have a plan and if it is reasonable. Kids who get jobs from programs tend to be happy customers and the school can recruit more students if they have happy graduates. So when you write this essay, keep this in mind.
Personally, the career essay should help you clarify what your plans are and how you go about them. Short term, think about getting a job in the industry you want to learn and develop in. Or if you have work experience, think about how you will lateral into a different field or how this degree will help you grow in your current industry.
Example - "Short term, I am looking to use my Masters in Management education to break into marketing at a large, multi national corporation, ideally in the consumer food industry. Long term, I want to work on creating ad campaigns and ultimately launch a new product."
Hope this helps some.