Emmet Fox 
The Mental Equivalent 
The Secret of Demonstration

The key to life is to build in the mental equivalents of what you want and to expunge the equivalents of what you do not want. How do you do it? You build in the mental equivalents by thinking quietly, constantly, and persistently of the kind of thing you want, and by thinking that has two qualities: clearness or definiteness, and interest. If you want to build anything into your life-if you want to bring health, right activity, your true place, inspiration; if you want to bring right companionship, and above all if you want understanding of God-form a mental equivalent of the thing which you want by thinking about it a great deal, by thinking clearly and with interest. Remember clarity and interest; those are the two poles.