The entire concept is very similar to Peter Pan and his never ending chant of "I do believe in fairies. I do, I do," when confronted with the possibility that Tinkerbell might die. So right there you see that it's not just about desiring something, it's about reaching as deeply down as you can and wanting it with your entire soul. About wanting it and believing without a doubt that you'll get it.
The idea that thoughts could affect the world outside of the head has been debunked and abused by critics as was expected considering that the idea is a new-aged one and has been steadily growing in popularity.
They say that thought cannot influence chance while others claim that chance is neither here nor there in the equation since it doesn't exist in the first place. Whatever the belief there are still a hefty number of followers out there who have studied and practiced the technique and sometimes received amazing results as rewards for their efforts.
The New York Times were the first to use the particular catchphrase Law of Attraction. Granted the phrase was used in 1879 and had very little to do with the actual exercise of the law of attraction but still, it was a huge turning point because at that moment people began to consider it as a more viable idea.
It was no longer the simple ramblings of crock-pots and psychics. It was a legitimate term with legitimate backing and while tat one sentence out of a thousand may not have revolutionized the minds of every critic within reading distance, it did start the stirring pot for something much bigger.
By 1902 electrical engineers, physicists, were beginning to put more credit behind the concept and in 1904 a movement began that would stretch over the next six years and pop up randomly every dozens of years thereafter. Thomas Troward, the poster child for the New Thought Movement, believed that your thoughts preceded any physical manifestations of them and that any action that the mind engages in is simply the seedling for something greater.
"A seedling which, when left alone, attracts the ingredients and nutrients that it needs to a physical manifestation." Bruce MacLelland said in his book "Prosperity Through Thought" Force, 'You are what you think, not what you think you are.' The quote pretty much summarizes the entire principle perfectly, a feat which authors who came before and after MacLelland, and who mentioned the subject too, were not able to accomplish nearly as well.