Powlison does a helpful Q&A on the concept of "the lusts of the flesh." Here is the first of fifteen questions. I'd encourage a careful reading and meditation upon these biblical, transforming concepts.
1. How does the New Testament commonly talk about what's wrong with people?
Lusts of the flesh (cravings or pleasures) is a summary term for what is wrong with us in God's eyes. In sin, people turn from God to serve what they want. By grace, people turn to God from their cravings. According to the Lord's assessment, we all formerly lived in the lusts of our flesh, indulging the desires of the flesh and the mind (Eph. 2:3). Those outside of Christ are thoroughly controlled by want they want. ("Of course I live for money, reputation, success, looks, and love. What else is there to live for?") And the most significant inner conflict in Christians is between what the Spirit wants and what we want.
But the term "lust" has become almost useless to modern readers of the Bible. It is reduced to sexual desire. Take a poll of the people in your church, asking them the meaning of "lusts of the flesh." Sex will appear on every list. Greed, pride, gluttonous craving, or mammon worship might be added in the answers of a few of the more thoughtful believers. But the subtleties and details are washed out, and a crucial biblical term for explaining human life languishes. In contrast, the New Testament writers use this term as a comprehensive category for the human dilemma! It will pay us to think carefully about its manifold meanings. We need to expand the meaning of a term that has been truncated and drained of significance. We need to learn to understand life though these lenses, and to use these categories skillfully.
The New Testament repeatedly focuses on the "lusts of the flesh" as a summary of what is wrong with the human heart that underlies bad behavior. For example, 1 John 2:16 contrasts the love of the Father with "all that is in the world, the lust of the flesh and the lust of the eyes and the boastful pride of life." (See also Rom. 13:14; Gal. 5:16-17; Eph. 2:2; 4:22; James 1:14-15; 4:1-3; 1 Pet. 1:14; 2 Pet. 1:4). This does not mean that the New Testament is internalistic. In each of these passages, behavior intimately connects to motive, and motive to behavior. Wise counselors follow the model of Scripture and move back and forth between lusts of the flesh and the tangible works of the flesh, between faith and the tangible fruit of the Spirit.
 The OT typically focuses on idolatry as the way people go astray. This doesn't mean that the OT is externalistic. Visible idolatry simple registers, for all to see, the failure to love the Lord God with heart, soul, mind, and might; it registers an internal defection. There are places where the problem of idolatry is turned into a metaphor for the most basic internalized sin (see Ezek. 14), and visible idolatry always expressed a defection of heart from God. There are places where the human heart is described as insane (Eccl. 9:3), evil (Gen. 6:5), full of cravings and lies (Num. 11-25). Idolatry can summarize every false, life-controlling master (1 John 5:21).
 We often hear warnings against externalistic religion. But internalistic religion creates equally serious problems. Christians often seek some experience of feeling, some sense of total brokenness, some comprehensive inward transformation--and miss that biblical change is practical and progressive, inside and out.