That is true if everything you make is thinking that a good outcome, it would be a good result. But if double-mind you don't pursue it because they do not become good the result.
Positive thinking attracts good things because you are in the good mood on what you are doing, that is why what is happening around you also doing the same thing that you do, so the result will be good also. For example, you wanted to save money, and you think that you could do it if you are going to work hard, and you just did, but if you are going to think the opposite, thinking that you can't then you are stopping yourself on making possibilities, it is more like turning it to impossibilities, and it is no good.