(Proverbs 25:28 KJV) He that hath no rule over his own spirit is like a city that is broken down, and without walls.
There was a time when any serious gathering of citizens living together would have some kind of “walls” (2346). Usually walls would not defeated a determined enemy with a large army. The walls would just slow him down. In small towns and villages the walls might be nothing more than a wooden fence. Picture the TV version of a fort in the west. The purpose was more to keep out the roving band or hasty bandits than to keep out artillery and scaling ladders.
That is one of the purposes of personal discipline. Any of us can be worn down by the determined onslaught of an enemy, be it the devil or our local building inspector. Discipline is what shields us from the quick raid that is looking for a foothold in our lives. Thus a conviction involving chastity will shield us from an office worker on the prowl but will do nothing against rape. Honesty will keep us from taking the money left on a desk but might give in to years of poverty.
So? We need to daily recommit ourselves to certain standards and disciplines so that the nose of Satan can’t get under the edge of our tent. The best defenses are deep stakes and a stomping boot.