Now, brethren, can we fight against and subdue ourselves? That is the greatest difficulty we ever encountered, and the most arduous warfare we over engaged in. This will apply most perfectly to the brethren who have gathered with the Saints. When we are out in the world we preach faith and repentance, so that the Saints bring the knowledge of first principles with them to the gathering-place. Your next step is to enter into the study of this. A man may learn letters and study all the various branches of scholastic education to the day of his death; but if he does not attain to strict self discipline, his learning will not amount to much. The catalogue of man’s discipline he must compile himself: he cannot be guided by any rule that others may lay down, but is placed under the necessity of tracing it himself through every avenue of his life. He is obliged to catechise and train himself, for he knows his own disposition the best—its fortified and unfortified parts. He is therefore the most fit to school himself, until every particle of the man is brought into subjection to the law of Christ.
Brigham Young, Journal of Discourses 6:315