Giving gratitude is one of the easiest and simplest ways to manifest your dreams. When you adopt an attitude of gratitude, you are sending a powerful message to the Universe about what it is that you want in your life. Giving thanks for all of the blessings in your life helps transform negative attitudes into positive ones. In turn, this raises your vibration and attracts positive experiences into your life. In the words of Walt Disney, “The more that you are in a state of gratitude, the more that you will attract things to be grateful for.”
It is all about consistency and frequency of vibration. Higher rate of vibration means higher speed of motion of energy. Manifestation is energy moving into form. Things take longer time to manifest on the physical plane because it exist at a lower rate of vibration. That is why consistency of faith is more important while existing on Earth. Our thoughts manifest as things instantaneously on the mental plane first before manifesting correspondingly on the physical plane over a period of time. If you could allow yourself to experience higher feelings consecutively for a certain period of time, your world will be bound to become a lot different than before in a much better way!
You claim that "positive thoughts always resulting in positive things" is not the basis of the LOA. In part you are correct. The foundational basis in science, as I alluded to in the article was that thought stuff particles travel through ether (not air) and interact with formless stuff to create whatever it is that you are thinking about. This was how "the law" started.
How To Manifest What I Desire