The word "natural" is a word that one can study for years and years, and one will find at the end of the study that there is no such thing as natural. There are natural inclinations to pleasure and comfort which clash with the still greater and deeper inclinations we have for more power and strength, for more light and for more life. So the inclinations can be divided into two aspects: the innermost inclinations, and the inclinations which one feels in everyday life. There is always a conflict between them; and the innermost inclinations are sometimes undermined by the outer inclinations. By learning self-discipline one learns to suppress the outer inclinations in order to make way for the inner inclinations to rise and to flourish, which finally culminates in what we call mastery.