When you learn a foreign language, especially a language that doesn't belong to your own language family, one of the things you discover is that languages work in different ways. In some languages (like Biblical Hebrew), the verb needs to come at the beginning of the sentence. In other languages (like Korean), the verb is delayed to the end. If you don't have a grasp of the way language works -- what we call its grammar -- you will never be able to speak that language properly.
Now, in my beginning grammar of New Testament Greek, we cover the entire indicative mood before we move on to the imperative mood. Moods are grammatical features of verbs that express the speaker's attitude toward the action. Two primary moods in language are the indicative and the imperative moods. The indicative mood is used to convey facts or opinions, such as "He's reading a book." In contrast, the imperative mood is used to give commands or requests, like "Read the book." Generally speaking, the majority of verbs in language are in the indicative mood. People tend to state information as facts more than they give commands, instructions, or directives.
Just as there are certain fundamental patterns in languages, so there are certain fundamental elements of the language of the gospel. Every important imperative of the gospel that tells us to obey is rooted in the indicatives of the gospel.

In other words, the Christian life is lived on the foundation of grace. It's because we've been justified in Christ that we begin to do things for Christ. The book of Ephesians is a good example. For 3 chapters Paul has been describing the new society (called the church) that God has brought forth through Jesus Christ, who died for sinners and was raised from death. But in chapters 4-6 Paul moves on from the reality of the new society to the new standards expected of it. He turns from exposition to exhortation, from indicatives (what Christ has done for us) to imperatives (what we must do in response). Theology moves from theory to practice. Thus in Eph. 4:1, Paul calls on the Ephesian believers to lead lives that are worthy of the calling to which God has called them. Any complacency when it comes to obedience is unworthy of the church's high calling.
Likewise, in his letter to the Romans, Paul moves in chapter 8 from Christian doctrine to Christian behavior, from people who believe in the gospel to people who live and adorn it. Indeed, the purpose of Christ's death was that "the righteous requirements of the law might be fully met in us" (Rom. 8:3). In Romans, Paul teaches not only the essense of the good news but also the essence of the good life. He never stops with mere knowledge. He gives people plain, practical, ethical teaching. The new life in Christ is a holy life, a life determined to please God by obeying his commandments.
We need to keep this biblical pattern clearly before us. In the Christian life, obedience is required. But it is also enabled. The Scriptures call us to hold the two together, which should not be difficult for Spirit-filled believers since the Holy Spirit himself is "the Spirit of truth" (John 14:17), and his firstfruit is "love" (Gal. 5:22).