What does the following quote mean: "There is no right or wrong only thinking makes it so"?

It is a theory that states that to believe in the essence of right and wrong, one simply has to think about it to make it so. For instance, if I murder somebody and think nothing of it, I could not think it is neither wrong nor right, it is just there. But, on the other hand, if i were to wonder if what i did was right or wrong, then an outcome may happen of being right or wrong.

I also wanted to show the sociological view of the right or wrong approach. In society, there are things called Norms and Transgressions. Norms are the expected behaviors of members of the society, while Transgressions are the breaking or not following of these rules or expected behaviors. A Norm is only created on the belief of right and wrong, so thus it is the societies basis and belief on what they think is right and wrong that they make their Norms.

So, if society did not believe in right and wrong, then there would be no Norms, and surely no Transgressions. Thus said, it is in societies power to dictate what is the right thing to do, and what would be not doing the right thing.