It is important to remember that thought is creative, irrespective of the quality of thought. However, even more important to remember is the fact that negative thinking leads to destruction, destruction of something that was previously positive. Negative thinking doesn't have principle, because it has no life force. It doesn't sustain, because in the end you fall victim to it - it destoys the destroyer, the one who's thought those thoughts.
Positive, and that is ... systematic, harmonious and constructive thinking does have principle, because it creates something out of nothing. No-thing is still something, just no perceptible with our senses, residing in the high-frequency, low-density realm that we call the Universal Consciousness or God.
So when you think positive and follow up that positive thinking with positive words and positive deeds, it will lead to a positive mindset and a positive life, because what you perceive on the outside is just a reflection of who you ALREADY ARE on the inside, not the other way round.
Keep that in mind with every thought you hold, every word you say, every deed you do, and remember that you are the Master of your own destiny - you create YOUR world as you go along. And now it's time to create it consciously. Enjoy!
As a follow-up on this topic, here are some more thoughts of mine.
"Thoughts become things" is the title of this third part. We know that thoughts are creative. However, this must not be confused, because not every thought turns into reality. Reality is a construct of many many thoughts combined. A single thought is way too weak in energy in order to affect anything - at least on our current level of existence and with our current level of concsiousness.
Charles Haanel talks about a predominant mental attitude, and that's what we create by thinking the same thought over and over again. It takes discipline to do that and not allow diverging or opposing thoughts to come to the surface. Once we have made this quality of thought our predominant mental attitude, we've created a habit. This habit then turns automatic if continued. Then it becomes us, and we have changed our neurological pathways and connections and created a sensitivity for the very thing we have thought about so many times.
Charles Haanel says later in the MKS that the Law of Attraction brings us our own, and that's exactly what is meant by this. Not what we think occasionally or think we deserve of what somebody else has; no, it brings us more of who we are already, but with the Master Key System we can change that. That's why we are here, and with a better understanding of how the processes of creative visualization work, it becomes much easier and more satisfying.