“We have to realize that this world in which we are living is not really our world. As Christians we live in it, and we must take our part in it. But we must not get excited about it; our biggest ambition must not be World Reform. What must matter most to us is that ‘our citizenship is in heaven’. If we are true Christians we know that this world will never be truly reformed. It cannot be reformed, because it is under the power and dominion of the devil. It is also under the ‘wrath of God’, under judgment, and will finally be destroyed. Therefore a man whose whole idea is to make the world a better place and who thinks that such a program makes him a Christian is denying the essential teaching of the Scripture. ‘Our citizenship is in heaven.’ The world is under ‘the god of this world’, the devil; and it is facing nothing but final disaster and final judgment. ‘Put on the breastplate of righteousness.’ Realize the state of the world in which you are living; do not look to it for your pleasure, your happiness, your joy. Use it, but do not abuse it. Keep your eye upon your heavenly home, the place to which you belong–‘set your affection on things above’.
Martyn Lloyd-Jones “Marching Orders” A sermon on Ephesians 6:14