When talking about query letters we often use the analogy of the job hunter. We say things like, "Your query letter is like the business suit you wear to a job interview. It's your first impression." But that analogy has never been quite right because you are not looking for a job, and the agent is not looking to hire you. In fact, it's just the opposite: You are looking to hire the agent. That being said, the agent still has the chance to say no, unlike many in today's job market.
So instead of thinking of your agent search as comparable to a job search, I think you should look at it as the search for an investor in your new business, because that is, in fact, what you're looking for. An investor will only agree to back your business if she feels it's going to be profitable for both of you. She has a certain level of financial success, a gain or return on her investment that she hopes to achieve, and her decision to invest or not invest in your business is based entirely on her personal feelings and experiences with the business you are proposing.
In other words, you might be pitching a profitable-looking business plan, but the investor might personally feel that it's not enough profit or simply not the type of business she wants to spend her money on, especially if she has six other business plans to consider.
Finding an agent to work with is about finding the right person to invest in your future as an author.