In the world — and yet not of the world

(J.C. Ryle, "Our Profession")

"You adulterous people, don't you know that friendship with the world is hatred toward God? Anyone who chooses to be a friend of the world, becomes an enemy of God." James 4:4

"My prayer is not that you take them out of the world — but that you protect them from the evil one." John 17:15

Happy, indeed, is that Christian who can be in the world — and yet not of the world; who can do his duty in it — and yet not be conformed to it; who can pass through it unmoved by . . .
  its smiles or its frowns,
  its flattery or its enmity,
  its open opposition or its hurtful ridicule,
  its sweets or its bitters,
  its gold or its sword!

When I think what the world is, and see what harm it has done and is doing to souls, I do not wonder that Scripture warns against loving it. Resolve to be very thorough, very decided, very watchful, very careful about the state of your soul.

Do not love the world or anything in the world. If anyone loves the world, the love of the Father is not in him. For everything in the world — the cravings of sinful man, the lust of his eyes and the boasting of what he has and does — comes not from the Father but from the world." 1 John 2:15-16