The belief is that if you continuously say something to yourself over time you will accept it to be true. Once you accept it to be true your mind will figure out a way to make it happen.
A personal Example:
So I had a thought about a month ago that I wanted to help people. Every night before bed I told myself that I would be the best life coach in the world. I had no idea how I would do it or if I even truly believed that I could.
By the end of the third week I was starting to believe that I could be a good life coach.
Towards the end of the fourth week I woke up with an idea to start this blog/forum. Currently this forum has no readers; only me. In a couple of months we will see if anyone else has found this blog/forum.