From Romans 7:23, we understand that the law of the mind is at war with the law of sin; and the law of sin seeks to make us its prisoner.  In verse 25 we read that we serve the law of God with the mind and with the flesh the law of sin.  The flesh here refers to that part of us that is unredeemed and still desires to sin.  The mind refers to that part of us that has been renewed, which wants to do good.  So, there is a constant battle within us, the flesh against our renewed mind, and the law of sin against the law of God.  And so, we struggle in our mind and in prayer to resist the pull of sin within us.

That sinful flesh within us (our unredeemed humanness) is fed by the things that Satan offers to us out of the evil world.  And we lust after those things.  That lust (the desire for those things), is conceived within our own heart and gives birth to sin (Ja. 1:14, 15).  Our lust is with the flesh (the body), to satisfy our appetite; with the eyes, to satisfy our greed; and with our pride, to satisfy our desire to be wise and important (Gen. 3:6).

But I must note also that even if the evil world weren’t offered to us we would still struggle with sin within us—with our selfishness, our love of ease, and with our lustful desires.  Yes, we constantly strive in prayer to resist these things.  Henceforth, we continue to wrestle within ourselves against our unwillingness to obey God, and to forgive others, and to pray for them.  And we struggle all through our prayers, to be awake and alert to the Spirit of God.

We wrestle in prayer with the goal to find victory over sin through Christ (Rom. 7:25), and to find peace and rest in Christ.  We wrestle with the view that we cannot win without Christ, that we are weak without Him.  Hence, we wrestle in prayer to find our weakness (that is, our sinfulness) and the strength of Christ.  We wrestle to be totally yielded to Him.