This is a very basic description of how positive thought works. That's why it is so very important to think positively. Affirmations are positive phrases that help us focus on what we want to be true in our lives. They are positive thoughts combined with intent. Gary Zukav talks a lot about intent.
Intent gives our thoughts a goal to work towards.
It boosts some extra positive energy into the mixture, as well. It's that plain and simple. Visualization is the icing on the cake. When you have a thought, and you intend for that thought to be brought into your life, and you can see yourself having that in your life, you will have it. Imagine that you want to lose 10 lbs.