I think it all depends on your level of awareness.
There was an example given in there, it said that if you focus on being late, you will attract things that will make you late to you. Now, if you don't worry about it, you won't.
Think about it this way. If you're focused on being late, you're going to notice any little thing that will delay you. if you don't care if you're late or not, you'll just go with the flow, and not notice any delays.
Now, a positive outlook never hurt anyone. I'm all for being positive. But I don't think that it works the way they say it does.