A man's mind may be compared to that of a garden. The garden can be intelligently cultivated or allowed to run wild. If no useful seeds are put into it, then an abundance of useless weed-seeds will fall in it and produce more of its kind. Just as a gardener cultivates his plot, keeping it free from weeds and growing the flowers and fruits which he requires, so may man tend the garden of his mind, weeding out all the wrong, useless, and impure thoughts , and cultivating toward perfection of the flowers and fruits of right, useful, and pure thoughts. By pursuing this process, a man sooner or later discovers that he is the master-gardener of his soul, the director of his life. He also reveals, within himself, the laws of thought, and understands, with ever-increasing accuracy, how the power of thought and elements of the mind operate in the shaping of his character, circumstances, and destiny.
This was drawn from "As a Man Thinketh" By James Allen