Agents and Query Letters

My experimentation with query letters is leaving me unsatisfied that I have gotten it down pat. I see dozens of examples of query letters sent to agents that ended up with the authors being published and wonder how to duplicate it with my own flair. I'm afraid of not getting it just right but at the same time, I have to have confidence in my work. So far those that know me usually give me compliments on my written work but I can't help but wonder if they simply say such things out of sympathy or simply because they are expected to like it. I know that I will be rejected by some agents but I only have so many to work with. I want to make the best work possible but sometimes this new world of agents and editors seems too much for me. However, the desire to be a published author is greater than my apprehension.