For the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh, for these are opposed to each other, to keep you from doing the things you want to do.This "flesh" has desires. It wants things. It's almost like it's alive. Some translations go with "sinful nature." That helps some.
In his book, Dynamics of Spiritual Life, Richard F. Lovelace says,
...the flesh might be called a "God complex."A "complex," in psychological terms, is "a core pattern of emotions, memories, perceptions, and wishes in the personal unconscious organized around a common theme, such as power or status."
He goes on to show how our "God complex" always backfires on us, because,
...the unconscious awareness of our independence from God and an unrelieved consciousness of guilt create a profound insecurity in the unbeliever or the Christian who is not walking in light. This insecurity generates a kind of compensatory egoism, self-oriented but somewhat different from serious pride. Thus much of what is called pride is actually not godlike self-admiration, but masked inferiority, insecurity and deep self-loathing. (90)The flesh often rules. We side with the flesh all the time and stiff-arm the Spirit. If Lovelace is right, how ironic that our desire to be our own gods (strong and capable and satisfied!) is what makes us so pathetically fragile and insecure.
The flesh is alive and kicking. No doubt about it. And it's killing us. But we don't owe the flesh anything. We don't have to bow the knee to its desires. We need to kill it...and we will live...for (the True) God.
Romans 8:12-13 So then, brothers, we are debtors, not to the flesh, to live according to the flesh. For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live.