Application essays suck. It's tough to write an in-depth essay about your career progress, why you want an MBA, why you think the school you're applying to is a good fit for you, what you want to do five years from now and what you want to do in the long term.
I don't know too many people who have clear-cut answers to these questions, and it wasn't/isn't the case for me. My own career progress was the result of a mix of strategy and opportunism. I didn't know enough about the options ten years ago to really know what I wanted, but it worked out pretty well for me nonetheless. Similarly, there are about five different avenues I can see myself taking after business school, all of which could be great. And in the long term, things get even foggier, but still there are some things I can see myself doing, and others I definitely don't want to do.
These are not the ingredients of an effective application essay. The trick, I think, is to impose form on the chaotic reality of the past and future. For example, I want to work in management consulting after I finish business school, and I also want to go the startup route. Both sound like great next steps after business school, but I didn't feel as though I could say this in my application essays. This would come across as indecisive, and moreover it would be tough to explain why these disparate career paths would be served by any one program.
To combine my prospective near-term goals, I explained in my essays why consulting would be a great next move for me, and how consulting experience combined with my MBA would help me succeed as an entrepreneur further down the road. In truth, I'm not certain that it's going to pan out that way, but the point of the essay isn't to convey what might be. It's to express your best guess as to how you think things will turn out, and to convey why an MBA is necessary for this to happen.
To build an effective application essay, you need to pick from the wide range of near/long term options that sound good to you - and stick with your choice. This is hard to do. I would get halfway through an essay and start second-guessing my choice. Is this really what I want to do? What about all of the other things that I might want to do? It doesn't matter, nobody is going to hold you to it. You have to pick something and stick with it for your essay to make sense and convey conviction.
I think it is a myth that successful people focus on a single long-term goal and spend their lives in pursuit of it. I think the reality is a lot less glamorous. If Bill Gates had applied to business school back in the 70s, would he have laid out his plan for world domination through buggy operating systems in his application essay? Probably not. He probably would have thought something like, "I'd love to use my programming skills to start a company, but I could also see myself running a research group at AT&T." His future would have been unclear, and he would have had to pick something to write a strong essay. We non-billionaires have to do the same thing.