Here’s an early Christian perspective on the Christian life in a non-Christian world and how we should view it.
But while living in both Greek and barbarian cities, as each have obtained by lot, and while following the local customs both in clothing and in diet and in the rest of life, they demonstrate the wonderful and most certainly strange character of their own citizenship. They live in their own countries, but as aliens. They share in everything as citizens and endure everything as foreigners. Every foreign country is their country, and every country is foreign. They marry like everyone, they bear children, but they do not expose their offspring. They set a common table, but not a common bed. They happen to be in the flesh but do not live according to the flesh. They spend time upon the earth, but have their citizenship in heaven.— Epistle to Diognetus 5.5-9