You will not be able to extemporize good thinking unless you have been in the habit of thinking and feeding your mind with abundant and nourishing food. Work hard at every available moment. Store your minds very richly, and then, like merchants with crowded warehouses, you will have goods ready for your customers, and having arranged your good things upon the shelves of your mind, you will be able to hand them down at any time without the laborious process of going to market, sorting, folding, and preparing. . . . Take it as a rule without exception, that to be able to overflow spontaneously you must be full.
HT: Trevin Wax