Well, it's pretty apparent, isn't it? And every person who discovered this believed (for a while) that he was the first one to work it out. We become what we think about.
Now, it stands to reason that a person who is thinking about a concrete and worthwhile goal is going to reach it, because that's what he's thinking about. And we become what we think about.
Conversely, the person who has no goal, who doesn't know where he's going, and whose thoughts must therefore be thoughts of confusion, anxiety, fear and worry - his life becomes one of frustration, fear, anxiety and worry. And if he thinks about nothing...he becomes nothing.
How does it work? Why do we become what we think about? Well, I'll tell you how it works, as far as we know. To do this, I want to tell you about a situation that parallels the human mind.
Suppose a farmer has some land, and it's good, fertile land. The land gives the farmer a choice; he may plant in that land whatever he chooses. The land doesn't care. It's up to the farmer to make a decision.
We're comparing the human mind with the land because the mind, like the land, doesn't care what you plant in it. It will return what you plant, but it doesn't care what you plant.
Now, let's say that the farmer has two seeds in his hand - one is a seed of corn, the other is nightshade, a deadly poison. He digs two little holes in the earth and he plants both seeds - one corn, the other nightshade. He covers up the holes, waters and takes care of the land...and what will happen? Invariably, the land will return what was planted. As it's written in the Bible,
"As ye sow, so shall ye reap."
Remember, the land doesn't care. It will return poison in just as wonderful abundance as it will corn. So up come the plants - one corn, one poison. The human mind is far more fertile, far more incredible and mysterious than the land, but it works the same way. It doesn't care what we plant...success...or failure. A concrete, worthwhile goal...or confusion, misunderstanding, fear, anxiety, and so on. But what we plant it must return to us.
You see, the human mind is the last great, unexplored continent on earth. It contains riches beyond our wildest dreams. It will return anything we want to plant.