Here’s an interesting quote by Charles Haanel:

“The greatest and most marvelous power which this “I” has been given is the power to think, but few people know how to think constructively, or correctly, consequently they achieve only indifferent results. Most people allow their thoughts to dwell on selfish purposes, the inevitable result of an infantile mind. When a mind becomes mature, it understands that the germ of defeat is in every selfish thought.

The trained mind knows that every transaction must benefit every person who is in any way connected with the transaction, and any attempt to profit by the weakness, ignorance or necessity of another will inevitably operate to his disadvantage.

This is because the individual is a part of the Universal. A part cannot antagonize any other part, but, on the contrary, the welfare of each part depends upon a recognition of the interest of the whole.

Those who recognize this principle have a great advantage in the affairs of life. They do not wear themselves out. They can eliminate vagrant thoughts with facility. They can readily concentrate to the highest possible degree on any subject. They do not waste time or money upon objects which can be of no possible benefit to them.

If you carry out this idea, beginning with small things which you know you can control and gradually increase the effort, but never under any circumstances allowing your “I” to be overruled, you will find that you can eventually control yourself, and many men and women have found to their sorrow that it is easier to control a kingdom that to control themselves.

But when you have learned to control yourself you will have found the “World Within” which controls the world without; you will have become irresistible; men and things will respond to your every wish without any apparent effort on your part.”