The assurance of the believer is not that God will save him even if he stops believing, but that God will keep him believing--God will sustain you in faith, he will make your hope firm and stable to the end. He will cause you to persevere.
John PiperJesus' teaching in general [implies] that happy and fulfilling sexual relations in marriage depend on each partner aiming to give satisfaction to the other. If it is the joy of each to make the other happy, a hundred problems will be solved before they happen.
John PiperThe suffering of sickness and the suffering of persecution have this in common: they are both intended by Satan for the destruction of our faith, and governed by God for the purifying of our faith... Christ sovereignly accomplishes His loving, purifying purpose, by overruling Satan's destructive attempts. Satan is always aiming to destroy our faith; but Christ magnifies His power in weakness.
John PiperSo, you have three possibilities in world missions. You can be a goer, a sender, or disobedient. The Bible does not assume that everyone goes. But it does assume that the ones who do not go care about goers and support goers and pray for goers and hold the rope of the goers.
John PiperSatan's aim is to destroy our joy and trust and delight in God, and to make God look worthless in the world's eyes. Everytime someone forsakes God for the world, gets angry at God when part of the world is taken away from them, they highlight the world as valuable... and everytime someone stays with God, when the world is taken away, and praises God, they highlight the value and glory of God.
John Piper