By the way, a "fleshly mind" or a "carnal mind" is not necessarily a reference to a sinful mind, only to a mind that is anchored in, and relying primarily upon, human powers of will, intellect and physical action in daily, practical living rather than upon the Holy Spirit. This sort of human-centered mind, because of its orientation away from God, quickly becomes fleshly in sinful ways, however.
But a Christian can be trying to work toward godly, spiritual ends by fleshly means, by means of human will-power, intellect and physical strength/action. Unfortunately, since like begets like, only a fleshly result is obtained. This fleshly sort of "Christian" living has been called "boot-strap Christianity" wherein a believer is constantly trying to pull himself up by his own boot-straps spiritually, which is impossible. This doesn't stop Christians from trying to do so - sometimes for decades - however.