Give no opportunity to the devil. Ephesians 4:27, R.S.V. AG 108.1
Satan's enmity against the human race is kindled because, through Christ, they are the objects of God's love and mercy. He desires to thwart the divine plan for man's redemption, to cast dishonor upon God, by defacing and defiling His handiwork; he would cause grief in heaven and fill the earth with woe and desolation. And he points to all his evil as the result of God's work in creating man. AG 108.2
It is the grace that Christ implants in the soul which creates in man enmity against Satan. Without this converting grace and renewing power, man would continue the captive of Satan, a servant ever ready to do his bidding. But the new principle in the soul creates conflict where hitherto had been peace. The power which Christ imparts, enables man to resist the tyrant and usurper. Whoever is seen to abhor sin instead of loving it, whoever resists and conquers those passions that have held sway within, displays the operation of a principle wholly from above.28The Great Controversy, 506. AG 108.3
Like a roaring lion, Satan is seeking for his prey. He tries his wiles upon every unsuspecting youth; there is safety only in Christ. It is through His grace alone that Satan can be successfully repulsed. Satan tells the young that there is time enough yet, that they may indulge in sin and vice this once and never again; but that one indulgence will poison their whole life. Do not once venture on forbidden ground. In this perilous day of evil, when allurements to vice and corruption are on every hand, let the earnest, heartfelt cry of the young be raised to heaven: “Wherewithal shall a young man cleanse his way?” And may his ears be open and his heart inclined to obey the instruction given in the answer: “By taking heed thereto according to thy word” (Psalm 119:9). The only safety for the youth in this age of pollution is to make God their trust. Without divine help they will be unable to control human passions and appetites. In Christ is the very help needed.... You can say with the apostle: “Nay, in all these things we are more than conquerors through him that loved us” (Romans 8:37). Again; “But I keep under my body, and bring it into subjection” (1 Corinthians 9:27).29Testimonies for the Church 2:409. AG 108.4