These two ideas form the general picture of what a believer’s overall duty is while left down here in this world. The example for our walk – our thoughts, our words, our actions – is always Jesus Christ (1 John 1:6). His life in the flesh as a man was perfect dependence on God (He is often seen in prayer) and perfect obedience to God (He never did His own will, but that of God, His Father). We may follow Paul, Peter, or John as an example, only because they are following Jesus as their example (Phil. 3:8-17). The responsibility of Christian discipleship is to take up our cross and follow Jesus (Mark 8:34, 10:21. Luke 9:23). The second general duty of every Christian is to constantly maintain in his/her mind and heart the expectation of the imminent return of Jesus Christ for His bride, the church (Titus 2:13). Those who have such a hope in Christ, purify themselves, just as He is pure (1 John 3:1-3) – maintaining this hope keeps the Christian separated from the world. This is how we are a light representing God in this dark world.
Some articles that discuss this topic in greater detail: