Those who would not fall a prey to Satan’s devices, must guard well the avenues of the soul; they must avoid reading, seeing, or hearing that which will suggest impure thoughts. The mind must not be left to dwell at random upon every subject that the enemy of souls may suggest. The heart must be faithfully sentineled, or evils without will awaken evils within, and the soul will wander in darkness.
(LYL 60.1)
Those who would have that wisdom which is from God must become fools in the sinful knowledge of this age, in order to be wise. They should shut their eyes, that they may see and learn no evil. They should close their ears, lest they hear that which is evil and obtain that knowledge which would stain their purity of thoughts and acts. And they should guard their tongues, lest they utter corrupt communications and guile be found in their mouths.
(LYL 60.2)
We are commanded to crucify the flesh, with the affections and lusts. How shall we do it? Shall we inflict pain on the body? No, but put to death the temptation to sin. The corrupt thought is to be expelled. Every thought is to be brought into captivity to Jesus Christ. All animal propensities are to be subjected to the higher powers of the soul. The love of God must reign supreme; Christ must occupy an undivided throne. Our bodies are to be regarded as His purchased possession. The members of the body are to become the instruments of righteousness.
(LYL 60.3)