Where do believers face most of their difficulty?
Believers face most of their difficulty from the Old Adam, not primarily from Satan. Though Satan has power, it is the Old Adam who inserts tempting thoughts, exploits moments of weakness, and constantly confronts them to follow the old Adamic nature, while the new nature is energized by the Holy Spirit.
Les explains that Paul's teaching is that believers now have two forces working within them. God reckons Old Adam to be absolutely dead, but in experience he is still there. Les says he does not mind the attacks of Satan half as much as the attacks of his Old Adam. As believers go through a week of life right here and now, most of their difficulty is not Satanic as much as Old Adam. Old Adam pops thoughts into our minds and catches us in moments of weakness. Les does not take away from Satan's power, but it is our Old Adam that constantly confronts us to still go the direction of the Old Adamic nature. Opposite that, believers have the new nature, which is energized by the Holy Spirit.