Romans 8 ends on a triumphant note, a fitting end to the first eight chapters of the letter (1:16-8:39 in particular). Paul begins to reflect on our current situation in contrast to the one that is coming. Currently, he and other Christians are suffering (8:18), but a "glory" is coming. If the default state of humanity is currently that "all have sinned and are lacking the glory of God" (3:23, author's translation), those in Christ look forward to a "glory that will be revealed" (8:17-18).
Christ has set in motion the complete solution to the problem Adam's sin created. Already can our sins be forgiven, already can we be considered "innocent" in God's divine court. Already does the Spirit give life to our mortal bodies here and now so that we can walk in newness of life. But we still await the complete redemption of the creation, currently enslaved to corruption and decay (8:21) and we await our full attainment of the glory of God lost through sin.
These are the verses where Paul connects the enslavement of human flesh to the enslavement of the material creation. Of course he would connect these, because in his categories they are made of the same weak materials. They are both subject to spiritual powers, whether to the power of Sin as they currently are or to the power of the Spirit as they can and will be. These metaphors work for us as well, although if we were to speak on a literal level we would no doubt talk of brain structures and quantum variables.
Our "flesh" will thus always be our weakest point, where we are speaking of our skin, the part of us that belongs to this world. It is not a matter of a sinful nature being eradicated or suppressed. It is a matter of whether we are controlled by the Spirit or not. If we are controlled by the Spirit, then the power of Sin over our flesh is dead. But the weakness of our flesh and its potential to sin is always as close as our loss of the Spirit.
In our current location, embodied in weakness, potentially empowered in Spirit, we will always face potential struggles. Some of these come from the world around us. But if we neglect our connection to the Holy Spirit, they will come from our bodies as well. We have two powerful intercessors in our fight. Christ's atonement has already interceded for our justification at God's right hand (8:34). But the Spirit gives constant intercession for us as well, even beyond what we know we need (8:26).
So we are conquerors in this fight against Sin, at least we should be. No one in the world can accuse us when the Judge of all is on our side. Human courts and human authorities can cause us trouble, but their judgments are not the ones that count. God has already arranged for us to be transformed into the same kind of resurrection body that Jesus already has. This is the original meaning of Romans 8:29, that we are predestined to be "conformed to the likeness of his Son." Paul's emphasis is not on determinism, on God's "predestination." The emphasis is on what God has in store for us because he knew us ahead of time.
Nor is Paul discussing the question of whether I can mess up what God has in store. When Paul says that nothing can separate us from the love of Christ, the context clearly has in mind the "present sufferings" he has been talking about all along (8:18). No external force "in all creation" has any power to dislodge us from the destiny in the kingdom toward which God is leading us (8:39).
Paul links the redemption of the enslaved creation to the redemption of bodies that will take place for those who are alive and remain at Christ's return (8:22-23). The created realm presumably came under the power of Sin when Adam sinned. Therefore, it seems very likely that Paul saw eternity and the kingdom of God being on a redeemed, transformed earth rather than in heaven.