Nature has so built us, that they can have control over the thoughts which reach our sub conscious mind, through the five senses. The sub conscious mind is a fertile garden, in which if good seeds are not sown, weeds will grow. In the same way, the thoughts that we have repeatedly in the conscious mind, whether positive or destructive, will manifest, because of the power of sub conscious mind which is influenced by these thoughts. Whenever there is a negative thought, replace it with a more powerful positive thought, accompanied by a strong positive emotion. Faith and love are the two positive and strong emotions.
Excerpt from “Think and Grow Rich” by Napoleon Hill